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	$244.57	6.147%	$259.6037	$259.60	$259.60	$259.60
Purchase #2	$102.33	4.260%	$106.6893	$106.69	$106.70	$106.70
Purchase #3	$196.73	13.319%	$222.9325	$222.93	$222.95	$222.90
Purchase #4	$14.44	13.199%	$16.3459	$16.35	$16.35	$16.30
Purchase #5	$88.86	8.861%	$96.7339	$96.73	$96.75	$96.70
Purchase #6	$158.33	9.190%	$172.8805	$172.88	$172.90	$172.90
Purchase #7	$95.49	5.129%	$100.3877	$100.39	$100.40	$100.40
7 purchase totals =	$900.75		$975.5735	$975.57	$975.65	$975.50