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	$166.67	10.861%	$184.772	$184.77	$184.75	$184.80
Purchase #2	$83.73	12.513%	$94.2071	$94.21	$94.20	$94.20
Purchase #3	$214.50	11.238%	$238.6055	$238.61	$238.60	$238.60
Purchase #4	$62.30	4.304%	$64.9814	$64.98	$65.00	$65.00
Purchase #5	$156.66	3.871%	$162.7243	$162.72	$162.70	$162.70
Purchase #6	$249.83	13.498%	$283.5521	$283.55	$283.55	$283.60
Purchase #7	$62.69	12.677%	$70.6372	$70.64	$70.65	$70.60
7 purchase totals =	$996.38		$1,099.4796	$1,099.48	$1,099.45	$1,099.50