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	$224.47	10.373%	$247.7543	$247.75	$247.75	$247.80
Purchase #2	$95.42	10.503%	$105.442	$105.44	$105.45	$105.40
Purchase #3	$86.85	3.400%	$89.8029	$89.80	$89.80	$89.80
Purchase #4	$65.82	5.717%	$69.5829	$69.58	$69.60	$69.60
Purchase #5	$82.59	4.850%	$86.5956	$86.60	$86.60	$86.60
Purchase #6	$90.52	5.251%	$95.2732	$95.27	$95.25	$95.30
Purchase #7	$137.96	9.754%	$151.4166	$151.42	$151.40	$151.40
7 purchase totals =	$783.63		$845.8675	$845.86	$845.85	$845.90