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	$141.73	4.145%	$147.6047	$147.60	$147.60	$147.60
Purchase #2	$71.79	3.269%	$74.1368	$74.14	$74.15	$74.10
Purchase #3	$199.45	13.737%	$226.8484	$226.85	$226.85	$226.80
Purchase #4	$63.38	13.414%	$71.8818	$71.88	$71.90	$71.90
Purchase #5	$50.93	11.638%	$56.8572	$56.86	$56.85	$56.90
Purchase #6	$153.72	12.845%	$173.4653	$173.47	$173.45	$173.50
Purchase #7	$173.33	4.199%	$180.6081	$180.61	$180.60	$180.60
7 purchase totals =	$854.33		$931.4023	$931.41	$931.40	$931.40