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	$135.37	7.209%	$145.1288	$145.13	$145.15	$145.10
Purchase #2	$160.43	8.824%	$174.5863	$174.59	$174.60	$174.60
Purchase #3	$159.58	13.231%	$180.694	$180.69	$180.70	$180.70
Purchase #4	$31.34	6.636%	$33.4197	$33.42	$33.40	$33.40
Purchase #5	$142.96	4.107%	$148.8314	$148.83	$148.85	$148.80
Purchase #6	$169.86	9.331%	$185.7096	$185.71	$185.70	$185.70
Purchase #7	$158.85	8.612%	$172.5302	$172.53	$172.55	$172.50
7 purchase totals =	$958.39		$1,040.9000	$1,040.90	$1,040.95	$1,040.80