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	$247.87	13.460%	$281.2333	$281.23	$281.25	$281.20
Purchase #2	$188.93	4.198%	$196.8613	$196.86	$196.85	$196.90
Purchase #3	$140.55	11.255%	$156.3689	$156.37	$156.35	$156.40
Purchase #4	$181.85	12.832%	$205.185	$205.19	$205.20	$205.20
Purchase #5	$36.76	11.395%	$40.9488	$40.95	$40.95	$40.90
Purchase #6	$79.96	13.461%	$90.7234	$90.72	$90.70	$90.70
Purchase #7	$195.46	8.805%	$212.6703	$212.67	$212.65	$212.70
7 purchase totals =	$1,071.38		$1,183.9910	$1,183.99	$1,183.95	$1,184.00