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	$98.95	12.206%	$111.0278	$111.03	$111.05	$111.00
Purchase #2	$175.78	4.793%	$184.2051	$184.21	$184.20	$184.20
Purchase #3	$82.47	9.498%	$90.303	$90.30	$90.30	$90.30
Purchase #4	$166.62	11.312%	$185.4681	$185.47	$185.45	$185.50
Purchase #5	$93.71	13.335%	$106.2062	$106.21	$106.20	$106.20
Purchase #6	$149.55	3.496%	$154.7783	$154.78	$154.80	$154.80
Purchase #7	$190.69	10.584%	$210.8726	$210.87	$210.85	$210.90
7 purchase totals =	$957.77		$1,042.8611	$1,042.87	$1,042.85	$1,042.90