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	$92.41	7.342%	$99.1947	$99.19	$99.20	$99.20
Purchase #2	$197.27	13.386%	$223.6766	$223.68	$223.70	$223.70
Purchase #3	$199.82	7.334%	$214.4748	$214.47	$214.45	$214.50
Purchase #4	$195.55	7.648%	$210.5057	$210.51	$210.50	$210.50
Purchase #5	$21.94	12.118%	$24.5987	$24.60	$24.60	$24.60
Purchase #6	$69.42	11.256%	$77.2339	$77.23	$77.25	$77.20
Purchase #7	$60.92	11.226%	$67.7589	$67.76	$67.75	$67.80
7 purchase totals =	$837.33		$917.4433	$917.44	$917.45	$917.50