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	$88.56	7.519%	$95.2188	$95.22	$95.20	$95.20
Purchase #2	$127.75	12.155%	$143.278	$143.28	$143.30	$143.30
Purchase #3	$25.33	10.681%	$28.0355	$28.04	$28.05	$28.00
Purchase #4	$231.53	3.193%	$238.9228	$238.92	$238.90	$238.90
Purchase #5	$123.97	6.245%	$131.7119	$131.71	$131.70	$131.70
Purchase #6	$34.92	9.348%	$38.1843	$38.18	$38.20	$38.20
Purchase #7	$46.89	10.652%	$51.8847	$51.88	$51.90	$51.90
7 purchase totals =	$678.95		$727.2360	$727.23	$727.25	$727.20