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	$63.84	12.601%	$71.8845	$71.88	$71.90	$71.90
Purchase #2	$25.89	5.620%	$27.345	$27.35	$27.35	$27.30
Purchase #3	$41.65	13.576%	$47.3044	$47.30	$47.30	$47.30
Purchase #4	$22.58	4.352%	$23.5627	$23.56	$23.55	$23.60
Purchase #5	$140.95	4.375%	$147.1166	$147.12	$147.10	$147.10
Purchase #6	$79.98	3.178%	$82.5218	$82.52	$82.50	$82.50
Purchase #7	$66.82	8.250%	$72.3327	$72.33	$72.35	$72.30
7 purchase totals =	$441.71		$472.0677	$472.06	$472.05	$472.00