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	$20.48	10.332%	$22.596	$22.60	$22.60	$22.60
Purchase #2	$25.38	4.711%	$26.5757	$26.58	$26.60	$26.60
Purchase #3	$159.85	7.317%	$171.5462	$171.55	$171.55	$171.50
Purchase #4	$140.87	12.346%	$158.2618	$158.26	$158.25	$158.30
Purchase #5	$126.56	10.831%	$140.2677	$140.27	$140.25	$140.30
Purchase #6	$166.90	11.767%	$186.5391	$186.54	$186.55	$186.50
Purchase #7	$72.39	8.342%	$78.4288	$78.43	$78.45	$78.40
7 purchase totals =	$712.43		$784.2153	$784.23	$784.25	$784.20