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	$57.61	3.464%	$59.6056	$59.61	$59.60	$59.60
Purchase #2	$99.98	12.290%	$112.2675	$112.27	$112.25	$112.30
Purchase #3	$237.53	10.528%	$262.5372	$262.54	$262.55	$262.50
Purchase #4	$131.73	11.193%	$146.4745	$146.47	$146.45	$146.50
Purchase #5	$159.48	6.117%	$169.2354	$169.24	$169.25	$169.20
Purchase #6	$123.90	11.678%	$138.369	$138.37	$138.35	$138.40
Purchase #7	$120.87	3.374%	$124.9482	$124.95	$124.95	$124.90
7 purchase totals =	$931.10		$1,013.4374	$1,013.45	$1,013.40	$1,013.40