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	$242.84	5.357%	$255.8489	$255.85	$255.85	$255.80
Purchase #2	$222.54	11.226%	$247.5223	$247.52	$247.50	$247.50
Purchase #3	$39.92	5.770%	$42.2234	$42.22	$42.20	$42.20
Purchase #4	$88.46	12.526%	$99.5405	$99.54	$99.55	$99.50
Purchase #5	$143.40	6.484%	$152.6981	$152.70	$152.70	$152.70
Purchase #6	$141.53	10.362%	$156.1953	$156.20	$156.20	$156.20
Purchase #7	$101.84	13.394%	$115.4804	$115.48	$115.50	$115.50
7 purchase totals =	$980.53		$1,069.5089	$1,069.51	$1,069.50	$1,069.40