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	$165.31	11.658%	$184.5818	$184.58	$184.60	$184.60
Purchase #2	$61.38	12.204%	$68.8708	$68.87	$68.85	$68.90
Purchase #3	$30.27	6.858%	$32.3459	$32.35	$32.35	$32.30
Purchase #4	$25.32	9.644%	$27.7619	$27.76	$27.75	$27.80
Purchase #5	$134.72	5.760%	$142.4799	$142.48	$142.50	$142.50
Purchase #6	$116.63	13.413%	$132.2736	$132.27	$132.25	$132.30
Purchase #7	$41.29	11.257%	$45.938	$45.94	$45.95	$45.90
7 purchase totals =	$574.92		$634.2519	$634.25	$634.25	$634.30