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	$40.65	10.769%	$45.0276	$45.03	$45.05	$45.00
Purchase #2	$142.99	6.551%	$152.3573	$152.36	$152.35	$152.40
Purchase #3	$91.36	12.380%	$102.6704	$102.67	$102.65	$102.70
Purchase #4	$171.89	9.386%	$188.0236	$188.02	$188.00	$188.00
Purchase #5	$46.40	13.784%	$52.7958	$52.80	$52.80	$52.80
Purchase #6	$59.31	13.427%	$67.2736	$67.27	$67.25	$67.30
Purchase #7	$205.89	7.593%	$221.5232	$221.52	$221.50	$221.50
7 purchase totals =	$758.49		$829.6715	$829.67	$829.60	$829.70