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	$155.77	12.620%	$175.4282	$175.43	$175.45	$175.40
Purchase #2	$9.28	13.224%	$10.5072	$10.51	$10.50	$10.50
Purchase #3	$108.91	3.740%	$112.9832	$112.98	$113.00	$113.00
Purchase #4	$236.97	7.569%	$254.9063	$254.91	$254.90	$254.90
Purchase #5	$38.35	11.594%	$42.7963	$42.80	$42.80	$42.80
Purchase #6	$79.92	12.807%	$90.1554	$90.16	$90.15	$90.20
Purchase #7	$138.32	12.416%	$155.4938	$155.49	$155.50	$155.50
7 purchase totals =	$767.52		$842.2704	$842.28	$842.30	$842.30