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	$80.52	13.556%	$91.4353	$91.44	$91.45	$91.40
Purchase #2	$142.32	3.134%	$146.7803	$146.78	$146.80	$146.80
Purchase #3	$27.51	11.270%	$30.6104	$30.61	$30.60	$30.60
Purchase #4	$161.25	7.614%	$173.5276	$173.53	$173.55	$173.50
Purchase #5	$243.92	8.774%	$265.3215	$265.32	$265.30	$265.30
Purchase #6	$53.40	11.505%	$59.5437	$59.54	$59.55	$59.50
Purchase #7	$231.88	11.364%	$258.2308	$258.23	$258.25	$258.20
7 purchase totals =	$940.80		$1,025.4496	$1,025.45	$1,025.50	$1,025.30