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	$81.72	11.630%	$91.224	$91.22	$91.20	$91.20
Purchase #2	$139.72	5.639%	$147.5988	$147.60	$147.60	$147.60
Purchase #3	$30.38	6.740%	$32.4276	$32.43	$32.45	$32.40
Purchase #4	$156.72	10.331%	$172.9107	$172.91	$172.90	$172.90
Purchase #5	$159.76	13.434%	$181.2222	$181.22	$181.20	$181.20
Purchase #6	$163.72	7.825%	$176.5311	$176.53	$176.55	$176.50
Purchase #7	$29.46	3.823%	$30.5863	$30.59	$30.60	$30.60
7 purchase totals =	$761.48		$832.5007	$832.50	$832.50	$832.40