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	$195.39	5.381%	$205.9039	$205.90	$205.90	$205.90
Purchase #2	$144.89	7.237%	$155.3757	$155.38	$155.40	$155.40
Purchase #3	$238.31	5.518%	$251.4599	$251.46	$251.45	$251.50
Purchase #4	$133.29	11.521%	$148.6463	$148.65	$148.65	$148.60
Purchase #5	$150.74	11.183%	$167.5973	$167.60	$167.60	$167.60
Purchase #6	$156.65	7.146%	$167.8442	$167.84	$167.85	$167.80
Purchase #7	$17.37	6.778%	$18.5473	$18.55	$18.55	$18.50
7 purchase totals =	$1,036.64		$1,115.3746	$1,115.38	$1,115.40	$1,115.30