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	$167.57	3.279%	$173.0646	$173.06	$173.05	$173.10
Purchase #2	$60.77	4.637%	$63.5879	$63.59	$63.60	$63.60
Purchase #3	$131.86	7.823%	$142.1754	$142.18	$142.20	$142.20
Purchase #4	$172.59	4.216%	$179.8664	$179.87	$179.85	$179.90
Purchase #5	$236.42	12.151%	$265.1474	$265.15	$265.15	$265.10
Purchase #6	$139.30	9.211%	$152.1309	$152.13	$152.15	$152.10
Purchase #7	$46.95	7.560%	$50.4994	$50.50	$50.50	$50.50
7 purchase totals =	$955.46		$1,026.4720	$1,026.48	$1,026.50	$1,026.50