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	$151.33	10.423%	$167.1031	$167.10	$167.10	$167.10
Purchase #2	$249.55	4.137%	$259.8739	$259.87	$259.85	$259.90
Purchase #3	$92.37	5.627%	$97.5677	$97.57	$97.55	$97.60
Purchase #4	$35.30	5.857%	$37.3675	$37.37	$37.35	$37.40
Purchase #5	$82.78	7.580%	$89.0547	$89.05	$89.05	$89.10
Purchase #6	$8.88	10.147%	$9.7811	$9.78	$9.80	$9.80
Purchase #7	$38.85	9.334%	$42.4763	$42.48	$42.50	$42.50
7 purchase totals =	$659.06		$703.2243	$703.22	$703.20	$703.40