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	$131.51	4.848%	$137.8856	$137.89	$137.90	$137.90
Purchase #2	$184.40	11.245%	$205.1358	$205.14	$205.15	$205.10
Purchase #3	$68.38	5.498%	$72.1395	$72.14	$72.15	$72.10
Purchase #4	$222.65	3.139%	$229.639	$229.64	$229.65	$229.60
Purchase #5	$85.39	9.270%	$93.3057	$93.31	$93.30	$93.30
Purchase #6	$25.41	11.830%	$28.416	$28.42	$28.40	$28.40
Purchase #7	$164.89	4.441%	$172.2128	$172.21	$172.20	$172.20
7 purchase totals =	$882.63		$938.7344	$938.75	$938.75	$938.60