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	$183.83	6.339%	$195.483	$195.48	$195.50	$195.50
Purchase #2	$152.56	5.415%	$160.8211	$160.82	$160.80	$160.80
Purchase #3	$58.41	7.814%	$62.9742	$62.97	$62.95	$63.00
Purchase #4	$15.37	7.193%	$16.4756	$16.48	$16.50	$16.50
Purchase #5	$99.80	11.762%	$111.5385	$111.54	$111.55	$111.50
Purchase #6	$95.29	9.768%	$104.5979	$104.60	$104.60	$104.60
Purchase #7	$134.29	12.432%	$150.9849	$150.98	$151.00	$151.00
7 purchase totals =	$739.55		$802.8752	$802.87	$802.90	$802.90