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	$63.73	13.553%	$72.3673	$72.37	$72.35	$72.40
Purchase #2	$152.39	7.855%	$164.3602	$164.36	$164.35	$164.40
Purchase #3	$156.37	12.301%	$175.6051	$175.61	$175.60	$175.60
Purchase #4	$142.39	12.740%	$160.5305	$160.53	$160.55	$160.50
Purchase #5	$121.25	8.618%	$131.6993	$131.70	$131.70	$131.70
Purchase #6	$162.69	13.381%	$184.4595	$184.46	$184.45	$184.50
Purchase #7	$176.46	11.540%	$196.8235	$196.82	$196.80	$196.80
7 purchase totals =	$975.28		$1,085.8454	$1,085.85	$1,085.80	$1,085.90