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	$184.28	7.764%	$198.5875	$198.59	$198.60	$198.60
Purchase #2	$92.47	12.227%	$103.7763	$103.78	$103.80	$103.80
Purchase #3	$197.97	11.662%	$221.0573	$221.06	$221.05	$221.10
Purchase #4	$11.72	3.484%	$12.1283	$12.13	$12.15	$12.10
Purchase #5	$167.30	13.157%	$189.3117	$189.31	$189.30	$189.30
Purchase #6	$151.72	5.378%	$159.8795	$159.88	$159.90	$159.90
Purchase #7	$110.65	7.602%	$119.0616	$119.06	$119.05	$119.10
7 purchase totals =	$916.11		$1,003.8022	$1,003.81	$1,003.85	$1,003.90