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	$229.90	11.742%	$256.8949	$256.89	$256.90	$256.90
Purchase #2	$78.27	6.623%	$83.4538	$83.45	$83.45	$83.50
Purchase #3	$199.60	6.281%	$212.1369	$212.14	$212.15	$212.10
Purchase #4	$66.31	12.644%	$74.6942	$74.69	$74.70	$74.70
Purchase #5	$53.45	7.153%	$57.2733	$57.27	$57.25	$57.30
Purchase #6	$159.40	6.854%	$170.3253	$170.33	$170.35	$170.30
Purchase #7	$179.62	11.770%	$200.7613	$200.76	$200.75	$200.80
7 purchase totals =	$966.55		$1,055.5397	$1,055.53	$1,055.55	$1,055.60