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	$205.70	5.330%	$216.6638	$216.66	$216.65	$216.70
Purchase #2	$143.83	4.612%	$150.4634	$150.46	$150.45	$150.50
Purchase #3	$17.32	9.489%	$18.9635	$18.96	$18.95	$19.00
Purchase #4	$113.52	9.545%	$124.3555	$124.36	$124.35	$124.40
Purchase #5	$149.79	12.476%	$168.4778	$168.48	$168.50	$168.50
Purchase #6	$246.69	12.812%	$278.2959	$278.30	$278.30	$278.30
Purchase #7	$53.74	7.169%	$57.5926	$57.59	$57.60	$57.60
7 purchase totals =	$930.59		$1,014.8125	$1,014.81	$1,014.80	$1,015.00