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	$238.79	12.797%	$269.348	$269.35	$269.35	$269.30
Purchase #2	$140.28	7.346%	$150.585	$150.59	$150.60	$150.60
Purchase #3	$71.98	4.620%	$75.3055	$75.31	$75.30	$75.30
Purchase #4	$201.37	11.189%	$223.9013	$223.90	$223.90	$223.90
Purchase #5	$52.75	13.560%	$59.9029	$59.90	$59.90	$59.90
Purchase #6	$243.87	13.510%	$276.8168	$276.82	$276.80	$276.80
Purchase #7	$54.32	7.224%	$58.2441	$58.24	$58.25	$58.20
7 purchase totals =	$1,003.36		$1,114.1036	$1,114.11	$1,114.10	$1,114.00