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	$31.44	6.208%	$33.3918	$33.39	$33.40	$33.40
Purchase #2	$222.85	7.315%	$239.1515	$239.15	$239.15	$239.20
Purchase #3	$56.51	6.574%	$60.225	$60.23	$60.25	$60.20
Purchase #4	$141.63	7.142%	$151.7452	$151.75	$151.75	$151.70
Purchase #5	$83.36	4.235%	$86.8903	$86.89	$86.90	$86.90
Purchase #6	$57.72	11.853%	$64.5616	$64.56	$64.55	$64.60
Purchase #7	$139.64	9.310%	$152.6405	$152.64	$152.65	$152.60
7 purchase totals =	$733.15		$788.6059	$788.61	$788.65	$788.60