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	$150.94	13.830%	$171.815	$171.82	$171.80	$171.80
Purchase #2	$153.90	6.590%	$164.042	$164.04	$164.05	$164.00
Purchase #3	$136.66	13.837%	$155.5696	$155.57	$155.55	$155.60
Purchase #4	$197.93	8.637%	$215.0252	$215.03	$215.05	$215.00
Purchase #5	$145.43	5.227%	$153.0316	$153.03	$153.05	$153.00
Purchase #6	$198.90	5.160%	$209.1632	$209.16	$209.15	$209.20
Purchase #7	$219.68	5.359%	$231.4527	$231.45	$231.45	$231.50
7 purchase totals =	$1,203.44		$1,300.0993	$1,300.10	$1,300.10	$1,300.10