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	$106.98	4.478%	$111.7706	$111.77	$111.75	$111.80
Purchase #2	$38.77	5.167%	$40.7732	$40.77	$40.75	$40.80
Purchase #3	$134.28	4.199%	$139.9184	$139.92	$139.90	$139.90
Purchase #4	$106.58	4.676%	$111.5637	$111.56	$111.55	$111.60
Purchase #5	$90.64	6.826%	$96.8271	$96.83	$96.85	$96.80
Purchase #6	$6.48	4.527%	$6.7733	$6.77	$6.75	$6.80
Purchase #7	$160.83	5.710%	$170.0134	$170.01	$170.00	$170.00
7 purchase totals =	$644.56		$677.6397	$677.63	$677.55	$677.70