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	$175.36	9.248%	$191.5773	$191.58	$191.60	$191.60
Purchase #2	$228.49	7.499%	$245.6245	$245.62	$245.60	$245.60
Purchase #3	$191.62	9.334%	$209.5058	$209.51	$209.50	$209.50
Purchase #4	$54.81	13.572%	$62.2488	$62.25	$62.25	$62.20
Purchase #5	$91.95	9.445%	$100.6347	$100.63	$100.65	$100.60
Purchase #6	$153.60	11.294%	$170.9476	$170.95	$170.95	$170.90
Purchase #7	$75.66	13.204%	$85.6501	$85.65	$85.65	$85.70
7 purchase totals =	$971.49		$1,066.1888	$1,066.19	$1,066.20	$1,066.10