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	$175.32	3.319%	$181.1389	$181.14	$181.15	$181.10
Purchase #2	$150.69	11.582%	$168.1429	$168.14	$168.15	$168.10
Purchase #3	$132.95	7.278%	$142.6261	$142.63	$142.65	$142.60
Purchase #4	$77.81	6.561%	$82.9151	$82.92	$82.90	$82.90
Purchase #5	$175.43	12.651%	$197.6236	$197.62	$197.60	$197.60
Purchase #6	$124.90	12.310%	$140.2752	$140.28	$140.30	$140.30
Purchase #7	$49.51	10.277%	$54.5981	$54.60	$54.60	$54.60
7 purchase totals =	$886.61		$967.3199	$967.33	$967.35	$967.20