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	$125.68	3.317%	$129.8488	$129.85	$129.85	$129.80
Purchase #2	$145.87	12.632%	$164.2963	$164.30	$164.30	$164.30
Purchase #3	$145.90	4.366%	$152.27	$152.27	$152.25	$152.30
Purchase #4	$87.39	13.320%	$99.0303	$99.03	$99.05	$99.00
Purchase #5	$31.39	3.778%	$32.5759	$32.58	$32.60	$32.60
Purchase #6	$112.25	4.587%	$117.3989	$117.40	$117.40	$117.40
Purchase #7	$149.91	6.808%	$160.1159	$160.12	$160.10	$160.10
7 purchase totals =	$798.39		$855.5361	$855.55	$855.55	$855.50