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	$189.90	11.410%	$211.5676	$211.57	$211.55	$211.60
Purchase #2	$64.89	9.832%	$71.27	$71.27	$71.25	$71.30
Purchase #3	$135.89	3.356%	$140.4505	$140.45	$140.45	$140.50
Purchase #4	$226.89	3.345%	$234.4795	$234.48	$234.50	$234.50
Purchase #5	$81.90	7.619%	$88.14	$88.14	$88.15	$88.10
Purchase #6	$114.45	5.766%	$121.0492	$121.05	$121.05	$121.00
Purchase #7	$58.53	13.601%	$66.4907	$66.49	$66.50	$66.50
7 purchase totals =	$872.45		$933.4475	$933.45	$933.45	$933.50