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	$90.86	9.110%	$99.1373	$99.14	$99.15	$99.10
Purchase #2	$18.37	13.830%	$20.9106	$20.91	$20.90	$20.90
Purchase #3	$151.51	11.301%	$168.6321	$168.63	$168.65	$168.60
Purchase #4	$235.96	9.110%	$257.456	$257.46	$257.45	$257.50
Purchase #5	$179.34	11.373%	$199.7363	$199.74	$199.75	$199.70
Purchase #6	$91.39	9.770%	$100.3188	$100.32	$100.30	$100.30
Purchase #7	$65.86	10.446%	$72.7397	$72.74	$72.75	$72.70
7 purchase totals =	$833.29		$918.9308	$918.94	$918.95	$918.80