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	$215.92	7.521%	$232.1593	$232.16	$232.15	$232.20
Purchase #2	$204.48	8.146%	$221.1369	$221.14	$221.15	$221.10
Purchase #3	$157.74	4.608%	$165.0087	$165.01	$165.00	$165.00
Purchase #4	$183.79	5.751%	$194.3598	$194.36	$194.35	$194.40
Purchase #5	$232.33	3.508%	$240.4801	$240.48	$240.50	$240.50
Purchase #6	$113.37	11.281%	$126.1593	$126.16	$126.15	$126.20
Purchase #7	$100.69	10.689%	$111.4528	$111.45	$111.45	$111.50
7 purchase totals =	$1,208.32		$1,290.7569	$1,290.76	$1,290.75	$1,290.90