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	$165.84	10.112%	$182.6097	$182.61	$182.60	$182.60
Purchase #2	$62.27	6.511%	$66.3244	$66.32	$66.30	$66.30
Purchase #3	$54.62	8.398%	$59.207	$59.21	$59.20	$59.20
Purchase #4	$95.63	5.142%	$100.5473	$100.55	$100.55	$100.50
Purchase #5	$192.52	11.179%	$214.0418	$214.04	$214.05	$214.00
Purchase #6	$237.40	7.325%	$254.7896	$254.79	$254.80	$254.80
Purchase #7	$50.83	5.345%	$53.5469	$53.55	$53.55	$53.50
7 purchase totals =	$859.11		$931.0667	$931.07	$931.05	$930.90