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	$24.95	5.546%	$26.3337	$26.33	$26.35	$26.30
Purchase #2	$146.65	13.478%	$166.4155	$166.42	$166.40	$166.40
Purchase #3	$108.78	13.582%	$123.5545	$123.55	$123.55	$123.60
Purchase #4	$123.40	11.576%	$137.6848	$137.68	$137.70	$137.70
Purchase #5	$12.93	5.224%	$13.6055	$13.61	$13.60	$13.60
Purchase #6	$114.90	11.530%	$128.148	$128.15	$128.15	$128.10
Purchase #7	$156.34	5.712%	$165.2701	$165.27	$165.25	$165.30
7 purchase totals =	$687.95		$761.0121	$761.01	$761.00	$761.00