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	$83.87	10.430%	$92.6176	$92.62	$92.60	$92.60
Purchase #2	$50.55	7.343%	$54.2619	$54.26	$54.25	$54.30
Purchase #3	$14.73	7.487%	$15.8328	$15.83	$15.85	$15.80
Purchase #4	$25.79	9.148%	$28.1493	$28.15	$28.15	$28.10
Purchase #5	$167.90	12.275%	$188.5097	$188.51	$188.50	$188.50
Purchase #6	$90.32	9.245%	$98.6701	$98.67	$98.65	$98.70
Purchase #7	$27.79	12.672%	$31.3115	$31.31	$31.30	$31.30
7 purchase totals =	$460.95		$509.3529	$509.35	$509.30	$509.30