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	$109.61	6.680%	$116.9319	$116.93	$116.95	$116.90
Purchase #2	$189.98	8.309%	$205.7654	$205.77	$205.75	$205.80
Purchase #3	$223.80	10.747%	$247.8518	$247.85	$247.85	$247.90
Purchase #4	$95.55	12.346%	$107.3466	$107.35	$107.35	$107.30
Purchase #5	$135.82	5.673%	$143.5251	$143.53	$143.55	$143.50
Purchase #6	$60.32	12.180%	$67.667	$67.67	$67.65	$67.70
Purchase #7	$196.34	7.759%	$211.574	$211.57	$211.55	$211.60
7 purchase totals =	$1,011.42		$1,100.6618	$1,100.67	$1,100.65	$1,100.70