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	$107.78	8.532%	$116.9758	$116.98	$117.00	$117.00
Purchase #2	$18.65	12.231%	$20.9311	$20.93	$20.95	$20.90
Purchase #3	$144.70	10.201%	$159.4608	$159.46	$159.45	$159.50
Purchase #4	$221.43	8.446%	$240.132	$240.13	$240.15	$240.10
Purchase #5	$240.32	10.502%	$265.5584	$265.56	$265.55	$265.60
Purchase #6	$32.85	7.570%	$35.3367	$35.34	$35.35	$35.30
Purchase #7	$179.27	9.669%	$196.6036	$196.60	$196.60	$196.60
7 purchase totals =	$945.00		$1,034.9984	$1,035.00	$1,035.05	$1,035.00