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	$247.68	5.824%	$262.1049	$262.10	$262.10	$262.10
Purchase #2	$145.89	3.248%	$150.6285	$150.63	$150.65	$150.60
Purchase #3	$58.45	12.504%	$65.7586	$65.76	$65.75	$65.80
Purchase #4	$226.39	6.261%	$240.5643	$240.56	$240.55	$240.60
Purchase #5	$137.57	3.141%	$141.8911	$141.89	$141.90	$141.90
Purchase #6	$58.76	10.368%	$64.8522	$64.85	$64.85	$64.90
Purchase #7	$139.26	13.592%	$158.1882	$158.19	$158.20	$158.20
7 purchase totals =	$1,014.00		$1,083.9878	$1,083.98	$1,084.00	$1,084.10