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	$184.93	5.178%	$194.5057	$194.51	$194.50	$194.50
Purchase #2	$59.45	10.731%	$65.8296	$65.83	$65.85	$65.80
Purchase #3	$150.61	3.489%	$155.8648	$155.86	$155.85	$155.90
Purchase #4	$170.89	9.832%	$187.6919	$187.69	$187.70	$187.70
Purchase #5	$66.58	8.114%	$71.9823	$71.98	$72.00	$72.00
Purchase #6	$196.31	11.292%	$218.4773	$218.48	$218.50	$218.50
Purchase #7	$205.46	11.752%	$229.6057	$229.61	$229.60	$229.60
7 purchase totals =	$1,034.23		$1,123.9573	$1,123.96	$1,124.00	$1,124.00