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	$159.61	4.131%	$166.2035	$166.20	$166.20	$166.20
Purchase #2	$60.65	8.645%	$65.8932	$65.89	$65.90	$65.90
Purchase #3	$66.94	7.596%	$72.0248	$72.02	$72.00	$72.00
Purchase #4	$122.25	5.345%	$128.7843	$128.78	$128.80	$128.80
Purchase #5	$161.35	7.495%	$173.4432	$173.44	$173.45	$173.40
Purchase #6	$156.67	9.711%	$171.8842	$171.88	$171.90	$171.90
Purchase #7	$222.51	9.413%	$243.4549	$243.45	$243.45	$243.50
7 purchase totals =	$949.98		$1,021.6881	$1,021.66	$1,021.70	$1,021.70