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	$11.30	12.753%	$12.7411	$12.74	$12.75	$12.70
Purchase #2	$83.57	8.728%	$90.864	$90.86	$90.85	$90.90
Purchase #3	$120.77	4.404%	$126.0887	$126.09	$126.10	$126.10
Purchase #4	$175.35	7.582%	$188.645	$188.65	$188.65	$188.60
Purchase #5	$57.86	11.459%	$64.4902	$64.49	$64.50	$64.50
Purchase #6	$145.63	11.545%	$162.443	$162.44	$162.45	$162.40
Purchase #7	$72.74	8.755%	$79.1084	$79.11	$79.10	$79.10
7 purchase totals =	$667.22		$724.3804	$724.38	$724.40	$724.30