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	$126.79	11.404%	$141.2491	$141.25	$141.25	$141.20
Purchase #2	$223.70	8.292%	$242.2492	$242.25	$242.25	$242.20
Purchase #3	$43.38	6.174%	$46.0583	$46.06	$46.05	$46.10
Purchase #4	$145.71	13.417%	$165.2599	$165.26	$165.25	$165.30
Purchase #5	$54.89	12.505%	$61.754	$61.75	$61.75	$61.80
Purchase #6	$146.47	12.192%	$164.3276	$164.33	$164.35	$164.30
Purchase #7	$6.48	7.208%	$6.9471	$6.95	$6.95	$6.90
7 purchase totals =	$747.42		$827.8452	$827.85	$827.85	$827.80