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	$111.26	7.646%	$119.7669	$119.77	$119.75	$119.80
Purchase #2	$155.86	13.389%	$176.7281	$176.73	$176.75	$176.70
Purchase #3	$215.53	3.741%	$223.593	$223.59	$223.60	$223.60
Purchase #4	$111.30	8.700%	$120.9831	$120.98	$121.00	$121.00
Purchase #5	$90.93	4.540%	$95.0582	$95.06	$95.05	$95.10
Purchase #6	$219.97	8.613%	$238.916	$238.92	$238.90	$238.90
Purchase #7	$50.83	7.873%	$54.8318	$54.83	$54.85	$54.80
7 purchase totals =	$955.68		$1,029.8771	$1,029.88	$1,029.90	$1,029.90