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	$57.50	8.530%	$62.4048	$62.40	$62.40	$62.40
Purchase #2	$151.53	12.305%	$170.1758	$170.18	$170.20	$170.20
Purchase #3	$58.79	13.473%	$66.7108	$66.71	$66.70	$66.70
Purchase #4	$174.49	12.506%	$196.3117	$196.31	$196.30	$196.30
Purchase #5	$237.77	4.553%	$248.5957	$248.60	$248.60	$248.60
Purchase #6	$190.72	13.206%	$215.9065	$215.91	$215.90	$215.90
Purchase #7	$155.52	10.529%	$171.8947	$171.89	$171.90	$171.90
7 purchase totals =	$1,026.32		$1,132.0000	$1,132.00	$1,132.00	$1,132.00