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	$228.29	7.194%	$244.7132	$244.71	$244.70	$244.70
Purchase #2	$183.83	6.670%	$196.0915	$196.09	$196.10	$196.10
Purchase #3	$111.76	10.110%	$123.0589	$123.06	$123.05	$123.10
Purchase #4	$222.76	4.125%	$231.9489	$231.95	$231.95	$231.90
Purchase #5	$26.42	7.790%	$28.4781	$28.48	$28.50	$28.50
Purchase #6	$114.98	4.133%	$119.7321	$119.73	$119.75	$119.70
Purchase #7	$164.78	9.256%	$180.032	$180.03	$180.05	$180.00
7 purchase totals =	$1,052.82		$1,124.0547	$1,124.05	$1,124.10	$1,124.00