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	$75.47	10.427%	$83.3393	$83.34	$83.35	$83.30
Purchase #2	$225.78	6.678%	$240.8576	$240.86	$240.85	$240.90
Purchase #3	$65.64	7.699%	$70.6936	$70.69	$70.70	$70.70
Purchase #4	$225.29	11.119%	$250.34	$250.34	$250.35	$250.30
Purchase #5	$60.98	7.108%	$65.3145	$65.31	$65.30	$65.30
Purchase #6	$149.63	8.474%	$162.3096	$162.31	$162.30	$162.30
Purchase #7	$146.28	9.835%	$160.6666	$160.67	$160.65	$160.70
7 purchase totals =	$949.07		$1,033.5212	$1,033.52	$1,033.50	$1,033.50