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	$96.49	9.122%	$105.2918	$105.29	$105.30	$105.30
Purchase #2	$83.74	8.840%	$91.1426	$91.14	$91.15	$91.10
Purchase #3	$86.44	11.164%	$96.0902	$96.09	$96.10	$96.10
Purchase #4	$151.66	4.192%	$158.0176	$158.02	$158.00	$158.00
Purchase #5	$102.96	4.429%	$107.5201	$107.52	$107.50	$107.50
Purchase #6	$143.25	5.768%	$151.5127	$151.51	$151.50	$151.50
Purchase #7	$72.29	8.112%	$78.1542	$78.15	$78.15	$78.20
7 purchase totals =	$736.83		$787.7292	$787.72	$787.70	$787.70