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	$12.40	6.659%	$13.2257	$13.23	$13.25	$13.20
Purchase #2	$183.96	3.278%	$189.9902	$189.99	$190.00	$190.00
Purchase #3	$182.32	7.563%	$196.1089	$196.11	$196.10	$196.10
Purchase #4	$209.75	6.170%	$222.6916	$222.69	$222.70	$222.70
Purchase #5	$155.62	6.185%	$165.2451	$165.25	$165.25	$165.20
Purchase #6	$80.53	13.703%	$91.565	$91.57	$91.55	$91.60
Purchase #7	$169.80	7.604%	$182.7116	$182.71	$182.70	$182.70
7 purchase totals =	$994.38		$1,061.5381	$1,061.55	$1,061.55	$1,061.50