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	$98.97	5.802%	$104.7122	$104.71	$104.70	$104.70
Purchase #2	$200.94	5.204%	$211.3969	$211.40	$211.40	$211.40
Purchase #3	$200.65	13.422%	$227.5812	$227.58	$227.60	$227.60
Purchase #4	$75.51	12.812%	$85.1843	$85.18	$85.20	$85.20
Purchase #5	$243.64	11.485%	$271.6221	$271.62	$271.60	$271.60
Purchase #6	$101.67	9.334%	$111.1599	$111.16	$111.15	$111.20
Purchase #7	$104.43	13.374%	$118.3965	$118.40	$118.40	$118.40
7 purchase totals =	$1,025.81		$1,130.0531	$1,130.05	$1,130.05	$1,130.10