Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$146.74	10.760%	$162.5292	$162.53	$162.55	$162.50
Purchase #2	$147.35	11.446%	$164.2157	$164.22	$164.20	$164.20
Purchase #3	$247.36	6.753%	$264.0642	$264.06	$264.05	$264.10
Purchase #4	$201.76	10.744%	$223.4371	$223.44	$223.45	$223.40
Purchase #5	$130.29	8.256%	$141.0467	$141.05	$141.05	$141.00
Purchase #6	$100.60	13.190%	$113.8691	$113.87	$113.85	$113.90
Purchase #7	$91.48	11.659%	$102.1457	$102.15	$102.15	$102.10
7 purchase totals =	$1,065.58		$1,171.3077	$1,171.32	$1,171.30	$1,171.20