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	$152.89	4.319%	$159.4933	$159.49	$159.50	$159.50
Purchase #2	$166.59	11.275%	$185.373	$185.37	$185.35	$185.40
Purchase #3	$154.72	13.537%	$175.6644	$175.66	$175.65	$175.70
Purchase #4	$141.31	7.256%	$151.5635	$151.56	$151.55	$151.60
Purchase #5	$199.92	3.112%	$206.1415	$206.14	$206.15	$206.10
Purchase #6	$165.71	13.455%	$188.0063	$188.01	$188.00	$188.00
Purchase #7	$204.68	10.466%	$226.1018	$226.10	$226.10	$226.10
7 purchase totals =	$1,185.82		$1,292.3438	$1,292.33	$1,292.30	$1,292.40