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	$185.34	8.153%	$200.4508	$200.45	$200.45	$200.50
Purchase #2	$50.52	9.711%	$55.426	$55.43	$55.45	$55.40
Purchase #3	$198.91	8.857%	$216.5275	$216.53	$216.55	$216.50
Purchase #4	$228.90	11.628%	$255.5165	$255.52	$255.50	$255.50
Purchase #5	$183.34	5.655%	$193.7079	$193.71	$193.70	$193.70
Purchase #6	$123.35	5.731%	$130.4192	$130.42	$130.40	$130.40
Purchase #7	$126.37	12.356%	$141.9843	$141.98	$142.00	$142.00
7 purchase totals =	$1,096.73		$1,194.0322	$1,194.04	$1,194.05	$1,194.00