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	$198.85	11.859%	$222.4316	$222.43	$222.45	$222.40
Purchase #2	$246.82	3.191%	$254.696	$254.70	$254.70	$254.70
Purchase #3	$245.77	3.242%	$253.7379	$253.74	$253.75	$253.70
Purchase #4	$152.69	4.481%	$159.532	$159.53	$159.55	$159.50
Purchase #5	$178.70	11.816%	$199.8152	$199.82	$199.80	$199.80
Purchase #6	$127.33	4.668%	$133.2738	$133.27	$133.25	$133.30
Purchase #7	$155.59	10.586%	$172.0608	$172.06	$172.05	$172.10
7 purchase totals =	$1,305.75		$1,395.5473	$1,395.55	$1,395.55	$1,395.50