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	$218.56	12.208%	$245.2418	$245.24	$245.25	$245.20
Purchase #2	$204.28	13.121%	$231.0836	$231.08	$231.10	$231.10
Purchase #3	$86.54	3.500%	$89.5689	$89.57	$89.55	$89.60
Purchase #4	$11.75	11.484%	$13.0994	$13.10	$13.10	$13.10
Purchase #5	$28.42	6.748%	$30.3378	$30.34	$30.35	$30.30
Purchase #6	$228.97	11.508%	$255.3199	$255.32	$255.30	$255.30
Purchase #7	$181.78	12.355%	$204.2389	$204.24	$204.25	$204.20
7 purchase totals =	$960.30		$1,068.8903	$1,068.89	$1,068.90	$1,068.80