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	$85.84	12.804%	$96.831	$96.83	$96.85	$96.80
Purchase #2	$52.49	9.379%	$57.413	$57.41	$57.40	$57.40
Purchase #3	$176.63	5.538%	$186.4118	$186.41	$186.40	$186.40
Purchase #4	$134.66	12.547%	$151.5558	$151.56	$151.55	$151.60
Purchase #5	$35.80	13.807%	$40.7429	$40.74	$40.75	$40.70
Purchase #6	$102.86	6.412%	$109.4554	$109.46	$109.45	$109.50
Purchase #7	$54.26	11.329%	$60.4071	$60.41	$60.40	$60.40
7 purchase totals =	$642.54		$702.8170	$702.82	$702.80	$702.80