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	$151.32	9.152%	$165.1688	$165.17	$165.15	$165.20
Purchase #2	$174.79	4.628%	$182.8793	$182.88	$182.90	$182.90
Purchase #3	$6.50	13.216%	$7.359	$7.36	$7.35	$7.40
Purchase #4	$204.87	11.864%	$229.1758	$229.18	$229.20	$229.20
Purchase #5	$124.86	9.243%	$136.4008	$136.40	$136.40	$136.40
Purchase #6	$71.54	10.314%	$78.9186	$78.92	$78.90	$78.90
Purchase #7	$100.85	9.649%	$110.581	$110.58	$110.60	$110.60
7 purchase totals =	$834.73		$910.4833	$910.49	$910.50	$910.60