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	$196.60	3.181%	$202.8538	$202.85	$202.85	$202.90
Purchase #2	$78.51	6.869%	$83.9029	$83.90	$83.90	$83.90
Purchase #3	$115.65	12.618%	$130.2427	$130.24	$130.25	$130.20
Purchase #4	$37.32	9.548%	$40.8833	$40.88	$40.90	$40.90
Purchase #5	$146.81	13.847%	$167.1388	$167.14	$167.15	$167.10
Purchase #6	$37.97	5.835%	$40.1855	$40.19	$40.20	$40.20
Purchase #7	$236.97	8.303%	$256.6456	$256.65	$256.65	$256.60
7 purchase totals =	$849.83		$921.8526	$921.85	$921.90	$921.80