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	$80.77	5.674%	$85.3529	$85.35	$85.35	$85.40
Purchase #2	$198.80	5.854%	$210.4378	$210.44	$210.45	$210.40
Purchase #3	$203.89	10.367%	$225.0273	$225.03	$225.05	$225.00
Purchase #4	$247.89	11.853%	$277.2724	$277.27	$277.25	$277.30
Purchase #5	$169.97	4.800%	$178.1286	$178.13	$178.15	$178.10
Purchase #6	$6.83	8.707%	$7.4247	$7.42	$7.40	$7.40
Purchase #7	$32.85	9.791%	$36.0663	$36.07	$36.05	$36.10
7 purchase totals =	$941.00		$1,019.7100	$1,019.71	$1,019.70	$1,019.70