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	$127.99	11.256%	$142.3966	$142.40	$142.40	$142.40
Purchase #2	$9.96	8.641%	$10.8206	$10.82	$10.80	$10.80
Purchase #3	$85.77	5.378%	$90.3827	$90.38	$90.40	$90.40
Purchase #4	$124.28	6.784%	$132.7112	$132.71	$132.70	$132.70
Purchase #5	$177.78	10.790%	$196.9625	$196.96	$196.95	$197.00
Purchase #6	$113.69	5.133%	$119.5257	$119.53	$119.55	$119.50
Purchase #7	$70.80	10.354%	$78.1306	$78.13	$78.15	$78.10
7 purchase totals =	$710.27		$770.9299	$770.93	$770.95	$770.90