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	$105.41	13.459%	$119.5971	$119.60	$119.60	$119.60
Purchase #2	$221.70	9.380%	$242.4955	$242.50	$242.50	$242.50
Purchase #3	$9.60	9.432%	$10.5055	$10.51	$10.50	$10.50
Purchase #4	$200.79	9.234%	$219.3309	$219.33	$219.35	$219.30
Purchase #5	$188.52	5.843%	$199.5352	$199.54	$199.55	$199.50
Purchase #6	$228.77	11.822%	$255.8152	$255.82	$255.80	$255.80
Purchase #7	$242.53	10.157%	$267.1638	$267.16	$267.15	$267.20
7 purchase totals =	$1,197.32		$1,314.4432	$1,314.46	$1,314.45	$1,314.40