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	$248.62	10.117%	$273.7729	$273.77	$273.75	$273.80
Purchase #2	$206.40	4.835%	$216.3794	$216.38	$216.40	$216.40
Purchase #3	$52.82	4.517%	$55.2059	$55.21	$55.20	$55.20
Purchase #4	$158.32	4.554%	$165.5299	$165.53	$165.55	$165.50
Purchase #5	$60.35	9.675%	$66.1889	$66.19	$66.20	$66.20
Purchase #6	$195.65	6.809%	$208.9718	$208.97	$208.95	$209.00
Purchase #7	$29.37	12.757%	$33.1167	$33.12	$33.10	$33.10
7 purchase totals =	$951.53		$1,019.1655	$1,019.17	$1,019.15	$1,019.20