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	$234.25	8.491%	$254.1402	$254.14	$254.15	$254.10
Purchase #2	$151.71	9.679%	$166.394	$166.39	$166.40	$166.40
Purchase #3	$197.72	11.682%	$220.8177	$220.82	$220.80	$220.80
Purchase #4	$106.43	4.574%	$111.2981	$111.30	$111.30	$111.30
Purchase #5	$69.94	12.403%	$78.6147	$78.61	$78.60	$78.60
Purchase #6	$145.62	3.437%	$150.625	$150.63	$150.65	$150.60
Purchase #7	$139.60	5.488%	$147.2612	$147.26	$147.25	$147.30
7 purchase totals =	$1,045.27		$1,129.1509	$1,129.15	$1,129.15	$1,129.10