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	$45.44	6.594%	$48.4363	$48.44	$48.45	$48.40
Purchase #2	$7.39	9.641%	$8.1025	$8.10	$8.10	$8.10
Purchase #3	$168.48	6.868%	$180.0512	$180.05	$180.05	$180.10
Purchase #4	$62.93	7.623%	$67.7272	$67.73	$67.75	$67.70
Purchase #5	$146.38	6.211%	$155.4717	$155.47	$155.45	$155.50
Purchase #6	$175.67	11.821%	$196.436	$196.44	$196.45	$196.40
Purchase #7	$131.77	8.796%	$143.3605	$143.36	$143.35	$143.40
7 purchase totals =	$738.06		$799.5854	$799.59	$799.60	$799.60