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	$35.84	4.482%	$37.4463	$37.45	$37.45	$37.40
Purchase #2	$203.33	9.432%	$222.5081	$222.51	$222.50	$222.50
Purchase #3	$89.75	10.491%	$99.1657	$99.17	$99.15	$99.20
Purchase #4	$126.53	13.430%	$143.523	$143.52	$143.50	$143.50
Purchase #5	$246.39	9.290%	$269.2796	$269.28	$269.30	$269.30
Purchase #6	$99.61	9.204%	$108.7781	$108.78	$108.80	$108.80
Purchase #7	$119.30	10.874%	$132.2727	$132.27	$132.25	$132.30
7 purchase totals =	$920.75		$1,012.9735	$1,012.98	$1,012.95	$1,013.00