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	$35.85	13.548%	$40.707	$40.71	$40.70	$40.70
Purchase #2	$117.35	4.851%	$123.0426	$123.04	$123.05	$123.00
Purchase #3	$227.76	7.260%	$244.2954	$244.30	$244.30	$244.30
Purchase #4	$226.71	12.850%	$255.8422	$255.84	$255.85	$255.80
Purchase #5	$186.66	13.522%	$211.9002	$211.90	$211.90	$211.90
Purchase #6	$42.41	8.584%	$46.0505	$46.05	$46.05	$46.10
Purchase #7	$96.64	8.785%	$105.1298	$105.13	$105.15	$105.10
7 purchase totals =	$933.38		$1,026.9677	$1,026.97	$1,027.00	$1,026.90