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	$173.45	3.288%	$179.153	$179.15	$179.15	$179.20
Purchase #2	$213.70	4.776%	$223.9063	$223.91	$223.90	$223.90
Purchase #3	$192.70	11.768%	$215.3769	$215.38	$215.40	$215.40
Purchase #4	$241.64	10.438%	$266.8624	$266.86	$266.85	$266.90
Purchase #5	$154.39	8.849%	$168.052	$168.05	$168.05	$168.10
Purchase #6	$100.79	10.165%	$111.0353	$111.04	$111.05	$111.00
Purchase #7	$98.52	11.201%	$109.5552	$109.56	$109.55	$109.60
7 purchase totals =	$1,175.19		$1,273.9411	$1,273.95	$1,273.95	$1,274.10