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	$141.63	7.556%	$152.3316	$152.33	$152.35	$152.30
Purchase #2	$74.67	9.584%	$81.8264	$81.83	$81.85	$81.80
Purchase #3	$89.83	11.684%	$100.3257	$100.33	$100.35	$100.30
Purchase #4	$198.33	6.806%	$211.8283	$211.83	$211.85	$211.80
Purchase #5	$104.44	3.504%	$108.0996	$108.10	$108.10	$108.10
Purchase #6	$128.89	6.500%	$137.2679	$137.27	$137.25	$137.30
Purchase #7	$166.53	7.460%	$178.9531	$178.95	$178.95	$179.00
7 purchase totals =	$904.32		$970.6326	$970.64	$970.70	$970.60