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	$190.96	3.857%	$198.3253	$198.33	$198.35	$198.30
Purchase #2	$158.71	7.766%	$171.0354	$171.04	$171.05	$171.00
Purchase #3	$228.25	11.485%	$254.4645	$254.46	$254.45	$254.50
Purchase #4	$229.48	7.297%	$246.2252	$246.23	$246.25	$246.20
Purchase #5	$57.83	12.467%	$65.0397	$65.04	$65.05	$65.00
Purchase #6	$20.96	7.216%	$22.4725	$22.47	$22.45	$22.50
Purchase #7	$132.31	6.441%	$140.8321	$140.83	$140.85	$140.80
7 purchase totals =	$1,018.50		$1,098.3947	$1,098.40	$1,098.45	$1,098.30