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	$113.53	12.587%	$127.82	$127.82	$127.80	$127.80
Purchase #2	$227.31	12.358%	$255.401	$255.40	$255.40	$255.40
Purchase #3	$53.94	13.630%	$61.292	$61.29	$61.30	$61.30
Purchase #4	$211.76	3.792%	$219.7899	$219.79	$219.80	$219.80
Purchase #5	$207.48	4.333%	$216.4701	$216.47	$216.45	$216.50
Purchase #6	$114.92	11.120%	$127.6991	$127.70	$127.70	$127.70
Purchase #7	$44.40	9.563%	$48.646	$48.65	$48.65	$48.60
7 purchase totals =	$973.34		$1,057.1181	$1,057.12	$1,057.10	$1,057.10