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	$241.43	9.607%	$264.6242	$264.62	$264.60	$264.60
Purchase #2	$195.88	7.173%	$209.9305	$209.93	$209.95	$209.90
Purchase #3	$28.54	11.731%	$31.888	$31.89	$31.90	$31.90
Purchase #4	$236.35	10.670%	$261.5685	$261.57	$261.55	$261.60
Purchase #5	$54.92	11.196%	$61.0688	$61.07	$61.05	$61.10
Purchase #6	$185.51	3.402%	$191.8211	$191.82	$191.80	$191.80
Purchase #7	$175.71	13.553%	$199.524	$199.52	$199.50	$199.50
7 purchase totals =	$1,118.34		$1,220.4251	$1,220.42	$1,220.35	$1,220.40