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	$165.82	4.869%	$173.8938	$173.89	$173.90	$173.90
Purchase #2	$15.96	10.110%	$17.5736	$17.57	$17.55	$17.60
Purchase #3	$250.74	9.854%	$275.4479	$275.45	$275.45	$275.40
Purchase #4	$117.65	8.815%	$128.0208	$128.02	$128.00	$128.00
Purchase #5	$108.56	4.668%	$113.6276	$113.63	$113.65	$113.60
Purchase #6	$12.92	3.283%	$13.3442	$13.34	$13.35	$13.30
Purchase #7	$116.97	5.743%	$123.6876	$123.69	$123.70	$123.70
7 purchase totals =	$788.62		$845.5955	$845.59	$845.60	$845.50