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	$214.50	12.289%	$240.8599	$240.86	$240.85	$240.90
Purchase #2	$71.76	12.660%	$80.8448	$80.84	$80.85	$80.80
Purchase #3	$61.52	4.444%	$64.2539	$64.25	$64.25	$64.30
Purchase #4	$85.69	6.132%	$90.9445	$90.94	$90.95	$90.90
Purchase #5	$193.85	7.383%	$208.1619	$208.16	$208.15	$208.20
Purchase #6	$75.64	8.420%	$82.0089	$82.01	$82.00	$82.00
Purchase #7	$127.48	7.595%	$137.1621	$137.16	$137.15	$137.20
7 purchase totals =	$830.44		$904.2360	$904.22	$904.20	$904.30