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	$137.46	10.654%	$152.105	$152.11	$152.10	$152.10
Purchase #2	$166.55	8.207%	$180.2188	$180.22	$180.20	$180.20
Purchase #3	$172.88	13.665%	$196.5041	$196.50	$196.50	$196.50
Purchase #4	$133.72	7.450%	$143.6821	$143.68	$143.70	$143.70
Purchase #5	$126.43	8.764%	$137.5103	$137.51	$137.50	$137.50
Purchase #6	$28.84	4.723%	$30.2021	$30.20	$30.20	$30.20
Purchase #7	$143.54	12.511%	$161.4983	$161.50	$161.50	$161.50
7 purchase totals =	$909.42		$1,001.7207	$1,001.72	$1,001.70	$1,001.70