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	$228.52	8.236%	$247.3409	$247.34	$247.35	$247.30
Purchase #2	$7.48	4.680%	$7.8301	$7.83	$7.85	$7.80
Purchase #3	$38.28	10.473%	$42.2891	$42.29	$42.30	$42.30
Purchase #4	$234.68	9.442%	$256.8385	$256.84	$256.85	$256.80
Purchase #5	$37.39	5.327%	$39.3818	$39.38	$39.40	$39.40
Purchase #6	$92.60	11.370%	$103.1286	$103.13	$103.15	$103.10
Purchase #7	$193.91	11.695%	$216.5878	$216.59	$216.60	$216.60
7 purchase totals =	$832.86		$913.3968	$913.40	$913.50	$913.30