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	$223.46	11.502%	$249.1624	$249.16	$249.15	$249.20
Purchase #2	$37.26	5.849%	$39.4393	$39.44	$39.45	$39.40
Purchase #3	$225.89	13.412%	$256.1864	$256.19	$256.20	$256.20
Purchase #4	$57.56	4.829%	$60.3396	$60.34	$60.35	$60.30
Purchase #5	$133.70	13.272%	$151.4447	$151.44	$151.45	$151.40
Purchase #6	$144.53	12.522%	$162.628	$162.63	$162.65	$162.60
Purchase #7	$92.77	5.675%	$98.0347	$98.03	$98.05	$98.00
7 purchase totals =	$915.17		$1,017.2351	$1,017.23	$1,017.30	$1,017.10