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	$43.40	11.816%	$48.5281	$48.53	$48.55	$48.50
Purchase #2	$175.72	9.776%	$192.8984	$192.90	$192.90	$192.90
Purchase #3	$34.96	11.300%	$38.9105	$38.91	$38.90	$38.90
Purchase #4	$36.84	3.268%	$38.0439	$38.04	$38.05	$38.00
Purchase #5	$226.58	9.123%	$247.2509	$247.25	$247.25	$247.30
Purchase #6	$55.82	6.250%	$59.3088	$59.31	$59.30	$59.30
Purchase #7	$153.54	9.528%	$168.1693	$168.17	$168.15	$168.20
7 purchase totals =	$726.86		$793.1099	$793.11	$793.10	$793.10