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	$122.48	11.401%	$136.4439	$136.44	$136.45	$136.40
Purchase #2	$150.95	6.501%	$160.7633	$160.76	$160.75	$160.80
Purchase #3	$241.47	9.624%	$264.7091	$264.71	$264.70	$264.70
Purchase #4	$63.27	13.731%	$71.9576	$71.96	$71.95	$72.00
Purchase #5	$188.60	12.571%	$212.3089	$212.31	$212.30	$212.30
Purchase #6	$127.93	9.260%	$139.7763	$139.78	$139.80	$139.80
Purchase #7	$113.70	5.175%	$119.584	$119.58	$119.60	$119.60
7 purchase totals =	$1,008.40		$1,105.5431	$1,105.54	$1,105.55	$1,105.60