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	$82.79	7.699%	$89.164	$89.16	$89.15	$89.20
Purchase #2	$118.79	13.681%	$135.0417	$135.04	$135.05	$135.00
Purchase #3	$165.57	4.123%	$172.3965	$172.40	$172.40	$172.40
Purchase #4	$193.45	11.423%	$215.5478	$215.55	$215.55	$215.50
Purchase #5	$81.94	8.400%	$88.823	$88.82	$88.80	$88.80
Purchase #6	$204.70	11.637%	$228.5209	$228.52	$228.50	$228.50
Purchase #7	$166.34	5.842%	$176.0576	$176.06	$176.05	$176.10
7 purchase totals =	$1,013.58		$1,105.5515	$1,105.55	$1,105.50	$1,105.50