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	$80.68	6.296%	$85.7596	$85.76	$85.75	$85.80
Purchase #2	$89.72	6.657%	$95.6927	$95.69	$95.70	$95.70
Purchase #3	$213.27	11.833%	$238.5062	$238.51	$238.50	$238.50
Purchase #4	$136.43	6.660%	$145.5162	$145.52	$145.50	$145.50
Purchase #5	$205.34	5.345%	$216.3154	$216.32	$216.30	$216.30
Purchase #6	$10.67	7.565%	$11.4772	$11.48	$11.50	$11.50
Purchase #7	$191.28	11.244%	$212.7875	$212.79	$212.80	$212.80
7 purchase totals =	$927.39		$1,006.0548	$1,006.07	$1,006.05	$1,006.10