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	$179.62	11.829%	$200.8672	$200.87	$200.85	$200.90
Purchase #2	$87.89	3.479%	$90.9477	$90.95	$90.95	$90.90
Purchase #3	$243.72	6.342%	$259.1767	$259.18	$259.20	$259.20
Purchase #4	$215.74	4.736%	$225.9574	$225.96	$225.95	$226.00
Purchase #5	$77.94	7.710%	$83.9492	$83.95	$83.95	$83.90
Purchase #6	$173.75	4.550%	$181.6556	$181.66	$181.65	$181.70
Purchase #7	$21.85	4.826%	$22.9045	$22.90	$22.90	$22.90
7 purchase totals =	$1,000.51		$1,065.4583	$1,065.47	$1,065.45	$1,065.50