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	$160.70	4.301%	$167.6117	$167.61	$167.60	$167.60
Purchase #2	$183.59	9.400%	$200.8475	$200.85	$200.85	$200.80
Purchase #3	$149.69	10.652%	$165.635	$165.64	$165.65	$165.60
Purchase #4	$142.97	6.333%	$152.0243	$152.02	$152.00	$152.00
Purchase #5	$231.96	7.474%	$249.2967	$249.30	$249.30	$249.30
Purchase #6	$204.92	3.518%	$212.1291	$212.13	$212.15	$212.10
Purchase #7	$178.65	9.711%	$195.9987	$196.00	$196.00	$196.00
7 purchase totals =	$1,252.48		$1,343.5430	$1,343.55	$1,343.55	$1,343.40