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	$65.30	10.154%	$71.9306	$71.93	$71.95	$71.90
Purchase #2	$140.34	7.547%	$150.9315	$150.93	$150.95	$150.90
Purchase #3	$114.56	12.852%	$129.2833	$129.28	$129.30	$129.30
Purchase #4	$107.60	6.423%	$114.5111	$114.51	$114.50	$114.50
Purchase #5	$73.77	11.423%	$82.1967	$82.20	$82.20	$82.20
Purchase #6	$19.38	10.853%	$21.4833	$21.48	$21.50	$21.50
Purchase #7	$61.43	5.471%	$64.7908	$64.79	$64.80	$64.80
7 purchase totals =	$582.38		$635.1273	$635.12	$635.20	$635.10