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	$43.45	9.485%	$47.5712	$47.57	$47.55	$47.60
Purchase #2	$93.41	10.418%	$103.1415	$103.14	$103.15	$103.10
Purchase #3	$156.86	9.676%	$172.0378	$172.04	$172.05	$172.00
Purchase #4	$230.61	8.547%	$250.3202	$250.32	$250.30	$250.30
Purchase #5	$33.55	11.506%	$37.4103	$37.41	$37.40	$37.40
Purchase #6	$133.68	12.530%	$150.4301	$150.43	$150.45	$150.40
Purchase #7	$36.53	4.818%	$38.29	$38.29	$38.30	$38.30
7 purchase totals =	$728.09		$799.2011	$799.20	$799.20	$799.10