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	$67.72	13.171%	$76.6394	$76.64	$76.65	$76.60
Purchase #2	$90.67	11.113%	$100.7462	$100.75	$100.75	$100.70
Purchase #3	$28.35	9.752%	$31.1147	$31.11	$31.10	$31.10
Purchase #4	$140.77	3.873%	$146.222	$146.22	$146.20	$146.20
Purchase #5	$19.44	7.146%	$20.8292	$20.83	$20.85	$20.80
Purchase #6	$14.97	12.638%	$16.8619	$16.86	$16.85	$16.90
Purchase #7	$206.85	6.312%	$219.9064	$219.91	$219.90	$219.90
7 purchase totals =	$568.77		$612.3198	$612.32	$612.30	$612.20