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	$61.61	9.584%	$67.5147	$67.51	$67.50	$67.50
Purchase #2	$46.30	8.782%	$50.3661	$50.37	$50.35	$50.40
Purchase #3	$29.34	10.198%	$32.3321	$32.33	$32.35	$32.30
Purchase #4	$245.92	7.156%	$263.518	$263.52	$263.50	$263.50
Purchase #5	$226.72	6.609%	$241.7039	$241.70	$241.70	$241.70
Purchase #6	$66.52	10.580%	$73.5578	$73.56	$73.55	$73.60
Purchase #7	$157.27	5.569%	$166.0284	$166.03	$166.05	$166.00
7 purchase totals =	$833.68		$895.0210	$895.02	$895.00	$895.00