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	$168.30	4.193%	$175.3568	$175.36	$175.35	$175.40
Purchase #2	$201.60	10.609%	$222.9877	$222.99	$223.00	$223.00
Purchase #3	$207.60	7.488%	$223.1451	$223.15	$223.15	$223.10
Purchase #4	$212.50	7.497%	$228.4311	$228.43	$228.45	$228.40
Purchase #5	$194.57	3.236%	$200.8663	$200.87	$200.85	$200.90
Purchase #6	$245.73	13.445%	$278.7684	$278.77	$278.75	$278.80
Purchase #7	$93.67	6.509%	$99.767	$99.77	$99.75	$99.80
7 purchase totals =	$1,323.97		$1,429.3224	$1,429.34	$1,429.30	$1,429.40