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	$180.72	5.287%	$190.2747	$190.27	$190.25	$190.30
Purchase #2	$87.73	7.753%	$94.5317	$94.53	$94.55	$94.50
Purchase #3	$205.66	8.408%	$222.9519	$222.95	$222.95	$223.00
Purchase #4	$130.75	7.806%	$140.9563	$140.96	$140.95	$141.00
Purchase #5	$137.98	7.416%	$148.2126	$148.21	$148.20	$148.20
Purchase #6	$183.39	3.757%	$190.28	$190.28	$190.30	$190.30
Purchase #7	$19.46	6.441%	$20.7134	$20.71	$20.70	$20.70
7 purchase totals =	$945.69		$1,007.9206	$1,007.91	$1,007.90	$1,008.00