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	$98.60	11.136%	$109.5801	$109.58	$109.60	$109.60
Purchase #2	$26.33	11.442%	$29.3427	$29.34	$29.35	$29.30
Purchase #3	$139.77	7.622%	$150.4233	$150.42	$150.40	$150.40
Purchase #4	$36.40	11.601%	$40.6228	$40.62	$40.60	$40.60
Purchase #5	$38.50	6.722%	$41.088	$41.09	$41.10	$41.10
Purchase #6	$37.56	10.135%	$41.3667	$41.37	$41.35	$41.40
Purchase #7	$46.36	13.674%	$52.6993	$52.70	$52.70	$52.70
7 purchase totals =	$423.52		$465.1229	$465.12	$465.10	$465.10