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	$173.26	9.665%	$190.0056	$190.01	$190.00	$190.00
Purchase #2	$39.33	6.313%	$41.8129	$41.81	$41.80	$41.80
Purchase #3	$171.63	8.651%	$186.4777	$186.48	$186.50	$186.50
Purchase #4	$148.43	5.525%	$156.6308	$156.63	$156.65	$156.60
Purchase #5	$132.87	5.477%	$140.1473	$140.15	$140.15	$140.10
Purchase #6	$234.74	4.289%	$244.808	$244.81	$244.80	$244.80
Purchase #7	$99.63	11.816%	$111.4023	$111.40	$111.40	$111.40
7 purchase totals =	$999.89		$1,071.2846	$1,071.29	$1,071.30	$1,071.20