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	$159.61	13.131%	$180.5684	$180.57	$180.55	$180.60
Purchase #2	$240.28	13.213%	$272.0282	$272.03	$272.05	$272.00
Purchase #3	$103.53	12.689%	$116.6669	$116.67	$116.65	$116.70
Purchase #4	$47.58	6.109%	$50.4867	$50.49	$50.50	$50.50
Purchase #5	$234.83	12.581%	$264.374	$264.37	$264.35	$264.40
Purchase #6	$54.58	9.593%	$59.8159	$59.82	$59.80	$59.80
Purchase #7	$147.59	13.644%	$167.7272	$167.73	$167.75	$167.70
7 purchase totals =	$988.00		$1,111.6673	$1,111.68	$1,111.65	$1,111.70