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	$118.46	10.354%	$130.7253	$130.73	$130.75	$130.70
Purchase #2	$163.95	8.282%	$177.5283	$177.53	$177.55	$177.50
Purchase #3	$229.46	11.745%	$256.4101	$256.41	$256.40	$256.40
Purchase #4	$79.69	13.835%	$90.7151	$90.72	$90.70	$90.70
Purchase #5	$70.42	11.274%	$78.3592	$78.36	$78.35	$78.40
Purchase #6	$97.46	7.190%	$104.4674	$104.47	$104.45	$104.50
Purchase #7	$20.80	7.700%	$22.4016	$22.40	$22.40	$22.40
7 purchase totals =	$780.24		$860.6070	$860.62	$860.60	$860.60