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	$188.34	4.286%	$196.4123	$196.41	$196.40	$196.40
Purchase #2	$48.79	9.668%	$53.507	$53.51	$53.50	$53.50
Purchase #3	$42.95	12.645%	$48.381	$48.38	$48.40	$48.40
Purchase #4	$74.90	10.551%	$82.8027	$82.80	$82.80	$82.80
Purchase #5	$156.64	11.503%	$174.6583	$174.66	$174.65	$174.70
Purchase #6	$56.74	3.819%	$58.9069	$58.91	$58.90	$58.90
Purchase #7	$103.41	6.595%	$110.2299	$110.23	$110.25	$110.20
7 purchase totals =	$671.77		$724.8981	$724.90	$724.90	$724.90