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	$110.81	12.780%	$124.9715	$124.97	$124.95	$125.00
Purchase #2	$37.89	7.137%	$40.5942	$40.59	$40.60	$40.60
Purchase #3	$243.28	13.587%	$276.3345	$276.33	$276.35	$276.30
Purchase #4	$163.75	9.275%	$178.9378	$178.94	$178.95	$178.90
Purchase #5	$65.80	9.484%	$72.0405	$72.04	$72.05	$72.00
Purchase #6	$79.91	12.300%	$89.7389	$89.74	$89.75	$89.70
Purchase #7	$155.56	5.796%	$164.5763	$164.58	$164.60	$164.60
7 purchase totals =	$857.00		$947.1937	$947.19	$947.25	$947.10