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	$137.84	13.426%	$156.3464	$156.35	$156.35	$156.30
Purchase #2	$146.96	5.684%	$155.3132	$155.31	$155.30	$155.30
Purchase #3	$126.62	11.623%	$141.337	$141.34	$141.35	$141.30
Purchase #4	$173.43	13.529%	$196.8933	$196.89	$196.90	$196.90
Purchase #5	$124.31	4.298%	$129.6528	$129.65	$129.65	$129.70
Purchase #6	$58.70	7.550%	$63.1319	$63.13	$63.15	$63.10
Purchase #7	$213.30	8.407%	$231.2321	$231.23	$231.25	$231.20
7 purchase totals =	$981.16		$1,073.9067	$1,073.90	$1,073.95	$1,073.80