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	$94.90	11.184%	$105.5136	$105.51	$105.50	$105.50
Purchase #2	$136.76	7.144%	$146.5301	$146.53	$146.55	$146.50
Purchase #3	$100.67	5.562%	$106.2693	$106.27	$106.25	$106.30
Purchase #4	$48.48	6.466%	$51.6147	$51.61	$51.60	$51.60
Purchase #5	$209.51	3.260%	$216.34	$216.34	$216.35	$216.30
Purchase #6	$219.74	9.553%	$240.7318	$240.73	$240.75	$240.70
Purchase #7	$222.72	7.819%	$240.1345	$240.13	$240.15	$240.10
7 purchase totals =	$1,032.78		$1,107.1340	$1,107.12	$1,107.15	$1,107.00