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	$95.37	10.872%	$105.7386	$105.74	$105.75	$105.70
Purchase #2	$248.46	3.790%	$257.8766	$257.88	$257.90	$257.90
Purchase #3	$33.97	10.288%	$37.4648	$37.46	$37.45	$37.50
Purchase #4	$159.93	13.811%	$182.0179	$182.02	$182.00	$182.00
Purchase #5	$63.31	9.440%	$69.2865	$69.29	$69.30	$69.30
Purchase #6	$149.55	11.113%	$166.1695	$166.17	$166.15	$166.20
Purchase #7	$47.39	13.771%	$53.9161	$53.92	$53.90	$53.90
7 purchase totals =	$797.98		$872.4700	$872.48	$872.45	$872.50