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	$242.54	7.831%	$261.5333	$261.53	$261.55	$261.50
Purchase #2	$144.85	12.376%	$162.7766	$162.78	$162.80	$162.80
Purchase #3	$152.51	12.586%	$171.7049	$171.70	$171.70	$171.70
Purchase #4	$202.40	10.505%	$223.6621	$223.66	$223.65	$223.70
Purchase #5	$16.35	5.565%	$17.2599	$17.26	$17.25	$17.30
Purchase #6	$167.82	7.555%	$180.4988	$180.50	$180.50	$180.50
Purchase #7	$116.42	5.793%	$123.1642	$123.16	$123.15	$123.20
7 purchase totals =	$1,042.89		$1,140.5998	$1,140.59	$1,140.60	$1,140.70