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	$53.52	11.359%	$59.5993	$59.60	$59.60	$59.60
Purchase #2	$69.71	3.233%	$71.9637	$71.96	$71.95	$72.00
Purchase #3	$249.56	9.499%	$273.2657	$273.27	$273.25	$273.30
Purchase #4	$19.81	12.753%	$22.3364	$22.34	$22.35	$22.30
Purchase #5	$91.36	9.394%	$99.9424	$99.94	$99.95	$99.90
Purchase #6	$210.28	13.363%	$238.3797	$238.38	$238.40	$238.40
Purchase #7	$174.70	12.422%	$196.4012	$196.40	$196.40	$196.40
7 purchase totals =	$868.94		$961.8884	$961.89	$961.90	$961.90