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	$225.88	10.510%	$249.62	$249.62	$249.60	$249.60
Purchase #2	$39.28	5.359%	$41.385	$41.39	$41.40	$41.40
Purchase #3	$200.54	4.174%	$208.9105	$208.91	$208.90	$208.90
Purchase #4	$220.36	13.152%	$249.3417	$249.34	$249.35	$249.30
Purchase #5	$230.29	9.241%	$251.5711	$251.57	$251.55	$251.60
Purchase #6	$37.78	6.313%	$40.1651	$40.17	$40.15	$40.20
Purchase #7	$46.44	11.677%	$51.8628	$51.86	$51.85	$51.90
7 purchase totals =	$1,000.57		$1,092.8562	$1,092.86	$1,092.80	$1,092.90