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	$117.53	6.190%	$124.8051	$124.81	$124.80	$124.80
Purchase #2	$165.31	13.812%	$188.1426	$188.14	$188.15	$188.10
Purchase #3	$208.27	11.136%	$231.4629	$231.46	$231.45	$231.50
Purchase #4	$141.73	8.288%	$153.4766	$153.48	$153.50	$153.50
Purchase #5	$126.53	3.627%	$131.1192	$131.12	$131.10	$131.10
Purchase #6	$136.72	7.615%	$147.1312	$147.13	$147.15	$147.10
Purchase #7	$177.59	7.601%	$191.0886	$191.09	$191.10	$191.10
7 purchase totals =	$1,073.68		$1,167.2262	$1,167.23	$1,167.25	$1,167.20