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	$174.49	8.383%	$189.1175	$189.12	$189.10	$189.10
Purchase #2	$240.81	10.558%	$266.2347	$266.23	$266.25	$266.20
Purchase #3	$92.25	13.667%	$104.8578	$104.86	$104.85	$104.90
Purchase #4	$191.65	7.771%	$206.5431	$206.54	$206.55	$206.50
Purchase #5	$190.49	13.733%	$216.65	$216.65	$216.65	$216.70
Purchase #6	$116.95	5.824%	$123.7612	$123.76	$123.75	$123.80
Purchase #7	$39.73	9.620%	$43.552	$43.55	$43.55	$43.60
7 purchase totals =	$1,046.37		$1,150.7163	$1,150.71	$1,150.70	$1,150.80