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	$188.52	6.431%	$200.6437	$200.64	$200.65	$200.60
Purchase #2	$119.66	3.555%	$123.9139	$123.91	$123.90	$123.90
Purchase #3	$243.32	13.505%	$276.1804	$276.18	$276.20	$276.20
Purchase #4	$161.80	10.404%	$178.6337	$178.63	$178.65	$178.60
Purchase #5	$227.34	12.624%	$256.0394	$256.04	$256.05	$256.00
Purchase #6	$82.28	3.470%	$85.1351	$85.14	$85.15	$85.10
Purchase #7	$134.35	5.723%	$142.0389	$142.04	$142.05	$142.00
7 purchase totals =	$1,157.27		$1,262.5851	$1,262.58	$1,262.65	$1,262.40