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	$31.68	6.432%	$33.7177	$33.72	$33.70	$33.70
Purchase #2	$9.46	10.531%	$10.4562	$10.46	$10.45	$10.50
Purchase #3	$145.45	5.306%	$153.1676	$153.17	$153.15	$153.20
Purchase #4	$202.58	11.449%	$225.7734	$225.77	$225.75	$225.80
Purchase #5	$103.32	7.661%	$111.2353	$111.24	$111.25	$111.20
Purchase #6	$78.33	13.547%	$88.9414	$88.94	$88.95	$88.90
Purchase #7	$28.26	10.530%	$31.2358	$31.24	$31.25	$31.20
7 purchase totals =	$599.08		$654.5274	$654.54	$654.50	$654.50