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	$156.69	7.464%	$168.3853	$168.39	$168.40	$168.40
Purchase #2	$159.58	3.429%	$165.052	$165.05	$165.05	$165.10
Purchase #3	$109.63	6.532%	$116.791	$116.79	$116.80	$116.80
Purchase #4	$100.89	3.502%	$104.4232	$104.42	$104.40	$104.40
Purchase #5	$76.40	6.165%	$81.1101	$81.11	$81.10	$81.10
Purchase #6	$240.70	5.740%	$254.5162	$254.52	$254.50	$254.50
Purchase #7	$223.70	7.780%	$241.1039	$241.10	$241.10	$241.10
7 purchase totals =	$1,067.59		$1,131.3817	$1,131.38	$1,131.35	$1,131.40