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	$7.60	4.409%	$7.9351	$7.94	$7.95	$7.90
Purchase #2	$91.95	7.241%	$98.6081	$98.61	$98.60	$98.60
Purchase #3	$105.28	5.872%	$111.462	$111.46	$111.45	$111.50
Purchase #4	$58.38	7.291%	$62.6365	$62.64	$62.65	$62.60
Purchase #5	$31.37	5.463%	$33.0837	$33.08	$33.10	$33.10
Purchase #6	$183.52	12.274%	$206.0452	$206.05	$206.05	$206.00
Purchase #7	$116.48	7.588%	$125.3185	$125.32	$125.30	$125.30
7 purchase totals =	$594.58		$645.0891	$645.10	$645.10	$645.00