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	$220.88	10.223%	$243.4606	$243.46	$243.45	$243.50
Purchase #2	$166.95	5.142%	$175.5346	$175.53	$175.55	$175.50
Purchase #3	$147.82	3.150%	$152.4763	$152.48	$152.50	$152.50
Purchase #4	$46.68	13.753%	$53.0999	$53.10	$53.10	$53.10
Purchase #5	$36.64	6.420%	$38.9923	$38.99	$39.00	$39.00
Purchase #6	$159.36	13.207%	$180.4067	$180.41	$180.40	$180.40
Purchase #7	$87.34	3.321%	$90.2406	$90.24	$90.25	$90.20
7 purchase totals =	$865.67		$934.2110	$934.21	$934.25	$934.20