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	$169.53	11.677%	$189.326	$189.33	$189.35	$189.30
Purchase #2	$204.54	4.244%	$213.2207	$213.22	$213.20	$213.20
Purchase #3	$99.52	6.405%	$105.8943	$105.89	$105.90	$105.90
Purchase #4	$125.70	4.212%	$130.9945	$130.99	$131.00	$131.00
Purchase #5	$147.30	7.115%	$157.7804	$157.78	$157.80	$157.80
Purchase #6	$82.52	10.735%	$91.3785	$91.38	$91.40	$91.40
Purchase #7	$168.85	7.741%	$181.9207	$181.92	$181.90	$181.90
7 purchase totals =	$997.96		$1,070.5151	$1,070.51	$1,070.55	$1,070.50