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	$89.30	5.141%	$93.8909	$93.89	$93.90	$93.90
Purchase #2	$105.81	5.801%	$111.948	$111.95	$111.95	$111.90
Purchase #3	$245.74	5.623%	$259.558	$259.56	$259.55	$259.60
Purchase #4	$140.88	7.313%	$151.1826	$151.18	$151.20	$151.20
Purchase #5	$39.53	13.538%	$44.8816	$44.88	$44.90	$44.90
Purchase #6	$216.37	13.681%	$245.9716	$245.97	$245.95	$246.00
Purchase #7	$250.53	11.817%	$280.1351	$280.14	$280.15	$280.10
7 purchase totals =	$1,088.16		$1,187.5678	$1,187.57	$1,187.60	$1,187.60