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	$64.75	12.265%	$72.6916	$72.69	$72.70	$72.70
Purchase #2	$206.56	6.272%	$219.5154	$219.52	$219.50	$219.50
Purchase #3	$186.67	10.745%	$206.7277	$206.73	$206.75	$206.70
Purchase #4	$160.56	7.188%	$172.1011	$172.10	$172.10	$172.10
Purchase #5	$210.50	10.125%	$231.8131	$231.81	$231.80	$231.80
Purchase #6	$76.39	5.715%	$80.7557	$80.76	$80.75	$80.80
Purchase #7	$59.37	3.443%	$61.4141	$61.41	$61.40	$61.40
7 purchase totals =	$964.80		$1,045.0187	$1,045.02	$1,045.00	$1,045.00