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	$135.30	7.115%	$144.9266	$144.93	$144.95	$144.90
Purchase #2	$22.52	10.555%	$24.897	$24.90	$24.90	$24.90
Purchase #3	$226.29	7.470%	$243.1939	$243.19	$243.20	$243.20
Purchase #4	$75.41	13.256%	$85.4063	$85.41	$85.40	$85.40
Purchase #5	$104.29	6.544%	$111.1147	$111.11	$111.10	$111.10
Purchase #6	$72.59	11.726%	$81.1019	$81.10	$81.10	$81.10
Purchase #7	$6.42	4.417%	$6.7036	$6.70	$6.70	$6.70
7 purchase totals =	$642.82		$697.3440	$697.34	$697.35	$697.30