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	$58.97	11.805%	$65.9314	$65.93	$65.95	$65.90
Purchase #2	$53.67	11.599%	$59.8952	$59.90	$59.90	$59.90
Purchase #3	$14.39	3.428%	$14.8833	$14.88	$14.90	$14.90
Purchase #4	$96.33	5.128%	$101.2698	$101.27	$101.25	$101.30
Purchase #5	$7.63	7.144%	$8.1751	$8.18	$8.20	$8.20
Purchase #6	$195.79	12.102%	$219.4845	$219.48	$219.50	$219.50
Purchase #7	$212.60	4.862%	$222.9366	$222.94	$222.95	$222.90
7 purchase totals =	$639.38		$692.5759	$692.58	$692.65	$692.60