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	$146.73	9.727%	$161.0024	$161.00	$161.00	$161.00
Purchase #2	$248.78	8.703%	$270.4313	$270.43	$270.45	$270.40
Purchase #3	$37.95	3.649%	$39.3348	$39.33	$39.35	$39.30
Purchase #4	$62.55	13.282%	$70.8579	$70.86	$70.85	$70.90
Purchase #5	$148.72	12.337%	$167.0676	$167.07	$167.05	$167.10
Purchase #6	$232.47	6.779%	$248.2291	$248.23	$248.25	$248.20
Purchase #7	$57.42	3.218%	$59.2678	$59.27	$59.25	$59.30
7 purchase totals =	$934.62		$1,016.1909	$1,016.19	$1,016.20	$1,016.20