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	$190.57	7.681%	$205.2077	$205.21	$205.20	$205.20
Purchase #2	$79.65	12.763%	$89.8157	$89.82	$89.80	$89.80
Purchase #3	$196.57	13.609%	$223.3212	$223.32	$223.30	$223.30
Purchase #4	$234.81	4.689%	$245.8202	$245.82	$245.80	$245.80
Purchase #5	$105.65	8.342%	$114.4633	$114.46	$114.45	$114.50
Purchase #6	$212.97	9.821%	$233.8858	$233.89	$233.90	$233.90
Purchase #7	$66.84	9.293%	$73.0514	$73.05	$73.05	$73.10
7 purchase totals =	$1,087.06		$1,185.5653	$1,185.57	$1,185.50	$1,185.60