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	$168.76	12.677%	$190.1537	$190.15	$190.15	$190.20
Purchase #2	$201.81	13.569%	$229.1936	$229.19	$229.20	$229.20
Purchase #3	$62.76	7.478%	$67.4532	$67.45	$67.45	$67.50
Purchase #4	$37.70	6.584%	$40.1822	$40.18	$40.20	$40.20
Purchase #5	$198.69	11.402%	$221.3446	$221.34	$221.35	$221.30
Purchase #6	$174.96	7.235%	$187.6184	$187.62	$187.60	$187.60
Purchase #7	$200.85	10.807%	$222.5559	$222.56	$222.55	$222.60
7 purchase totals =	$1,045.53		$1,158.5016	$1,158.49	$1,158.50	$1,158.60