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	$142.27	7.160%	$152.4565	$152.46	$152.45	$152.50
Purchase #2	$173.65	8.211%	$187.9084	$187.91	$187.90	$187.90
Purchase #3	$25.99	7.221%	$27.8667	$27.87	$27.85	$27.90
Purchase #4	$168.86	10.442%	$186.4924	$186.49	$186.50	$186.50
Purchase #5	$156.59	10.261%	$172.6577	$172.66	$172.65	$172.70
Purchase #6	$170.29	4.223%	$177.4813	$177.48	$177.50	$177.50
Purchase #7	$54.78	11.478%	$61.0676	$61.07	$61.05	$61.10
7 purchase totals =	$892.43		$965.9306	$965.94	$965.90	$966.10