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	$219.67	12.660%	$247.4802	$247.48	$247.50	$247.50
Purchase #2	$122.61	12.454%	$137.8798	$137.88	$137.90	$137.90
Purchase #3	$140.33	12.867%	$158.3863	$158.39	$158.40	$158.40
Purchase #4	$57.54	12.161%	$64.5374	$64.54	$64.55	$64.50
Purchase #5	$48.88	3.133%	$50.4114	$50.41	$50.40	$50.40
Purchase #6	$211.27	10.675%	$233.8231	$233.82	$233.80	$233.80
Purchase #7	$118.39	11.747%	$132.2973	$132.30	$132.30	$132.30
7 purchase totals =	$918.69		$1,024.8155	$1,024.82	$1,024.85	$1,024.80