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	$199.61	8.837%	$217.2495	$217.25	$217.25	$217.20
Purchase #2	$24.42	3.432%	$25.2581	$25.26	$25.25	$25.30
Purchase #3	$79.58	12.173%	$89.2673	$89.27	$89.25	$89.30
Purchase #4	$83.95	6.804%	$89.662	$89.66	$89.65	$89.70
Purchase #5	$201.71	6.805%	$215.4364	$215.44	$215.45	$215.40
Purchase #6	$173.39	3.630%	$179.6841	$179.68	$179.70	$179.70
Purchase #7	$71.46	6.209%	$75.897	$75.90	$75.90	$75.90
7 purchase totals =	$834.12		$892.4544	$892.46	$892.45	$892.50