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	$58.98	6.637%	$62.8945	$62.89	$62.90	$62.90
Purchase #2	$137.73	12.543%	$155.0055	$155.01	$155.00	$155.00
Purchase #3	$220.78	5.415%	$232.7352	$232.74	$232.75	$232.70
Purchase #4	$153.74	5.756%	$162.5893	$162.59	$162.60	$162.60
Purchase #5	$93.54	7.787%	$100.824	$100.82	$100.80	$100.80
Purchase #6	$54.86	7.676%	$59.0711	$59.07	$59.05	$59.10
Purchase #7	$213.65	12.653%	$240.6831	$240.68	$240.70	$240.70
7 purchase totals =	$933.28		$1,013.8027	$1,013.80	$1,013.80	$1,013.80