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	$119.38	11.773%	$133.4346	$133.43	$133.45	$133.40
Purchase #2	$75.79	9.249%	$82.7998	$82.80	$82.80	$82.80
Purchase #3	$135.38	9.634%	$148.4225	$148.42	$148.40	$148.40
Purchase #4	$175.92	9.108%	$191.9428	$191.94	$191.95	$191.90
Purchase #5	$233.37	7.146%	$250.0466	$250.05	$250.05	$250.00
Purchase #6	$246.75	3.460%	$255.2876	$255.29	$255.30	$255.30
Purchase #7	$91.99	9.442%	$100.6757	$100.68	$100.70	$100.70
7 purchase totals =	$1,078.58		$1,162.6096	$1,162.61	$1,162.65	$1,162.50