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	$173.39	5.827%	$183.4934	$183.49	$183.50	$183.50
Purchase #2	$227.37	12.334%	$255.4138	$255.41	$255.40	$255.40
Purchase #3	$116.55	13.661%	$132.4719	$132.47	$132.45	$132.50
Purchase #4	$231.78	7.215%	$248.5029	$248.50	$248.50	$248.50
Purchase #5	$86.78	10.431%	$95.832	$95.83	$95.85	$95.80
Purchase #6	$111.54	11.212%	$124.0459	$124.05	$124.05	$124.00
Purchase #7	$23.80	11.270%	$26.4823	$26.48	$26.50	$26.50
7 purchase totals =	$971.21		$1,066.2422	$1,066.23	$1,066.25	$1,066.20