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	$130.65	3.624%	$135.3848	$135.38	$135.40	$135.40
Purchase #2	$222.44	11.389%	$247.7737	$247.77	$247.75	$247.80
Purchase #3	$88.50	4.154%	$92.1763	$92.18	$92.20	$92.20
Purchase #4	$196.66	9.512%	$215.3663	$215.37	$215.35	$215.40
Purchase #5	$69.83	4.284%	$72.8215	$72.82	$72.80	$72.80
Purchase #6	$233.27	8.650%	$253.4479	$253.45	$253.45	$253.40
Purchase #7	$44.94	3.554%	$46.5372	$46.54	$46.55	$46.50
7 purchase totals =	$986.29		$1,063.5077	$1,063.51	$1,063.50	$1,063.50