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	$71.33	10.510%	$78.8268	$78.83	$78.85	$78.80
Purchase #2	$10.91	10.596%	$12.066	$12.07	$12.05	$12.10
Purchase #3	$100.96	8.373%	$109.4134	$109.41	$109.40	$109.40
Purchase #4	$30.50	4.844%	$31.9774	$31.98	$32.00	$32.00
Purchase #5	$173.45	8.789%	$188.6945	$188.69	$188.70	$188.70
Purchase #6	$239.94	3.220%	$247.6661	$247.67	$247.65	$247.70
Purchase #7	$108.27	11.788%	$121.0329	$121.03	$121.05	$121.00
7 purchase totals =	$735.36		$789.6771	$789.68	$789.70	$789.70