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	$124.61	7.402%	$133.8336	$133.83	$133.85	$133.80
Purchase #2	$34.95	12.737%	$39.4016	$39.40	$39.40	$39.40
Purchase #3	$233.94	5.817%	$247.5483	$247.55	$247.55	$247.50
Purchase #4	$156.88	5.747%	$165.8959	$165.90	$165.90	$165.90
Purchase #5	$52.85	7.520%	$56.8243	$56.82	$56.80	$56.80
Purchase #6	$137.26	13.492%	$155.7791	$155.78	$155.80	$155.80
Purchase #7	$214.55	5.297%	$225.9147	$225.91	$225.90	$225.90
7 purchase totals =	$955.04		$1,025.1975	$1,025.19	$1,025.20	$1,025.10