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	$147.83	3.702%	$153.3027	$153.30	$153.30	$153.30
Purchase #2	$93.27	8.773%	$101.4526	$101.45	$101.45	$101.50
Purchase #3	$80.71	11.475%	$89.9715	$89.97	$89.95	$90.00
Purchase #4	$64.45	3.331%	$66.5968	$66.60	$66.60	$66.60
Purchase #5	$167.72	8.222%	$181.5099	$181.51	$181.50	$181.50
Purchase #6	$65.82	8.519%	$71.4272	$71.43	$71.45	$71.40
Purchase #7	$37.28	5.413%	$39.298	$39.30	$39.30	$39.30
7 purchase totals =	$657.08		$703.5587	$703.56	$703.55	$703.60