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	$126.44	8.774%	$137.5338	$137.53	$137.55	$137.50
Purchase #2	$37.59	6.769%	$40.1345	$40.13	$40.15	$40.10
Purchase #3	$129.35	13.122%	$146.3233	$146.32	$146.30	$146.30
Purchase #4	$152.80	3.523%	$158.1831	$158.18	$158.20	$158.20
Purchase #5	$23.73	3.445%	$24.5475	$24.55	$24.55	$24.50
Purchase #6	$223.52	3.445%	$231.2203	$231.22	$231.20	$231.20
Purchase #7	$142.50	7.198%	$152.7572	$152.76	$152.75	$152.80
7 purchase totals =	$835.93		$890.6997	$890.69	$890.70	$890.60