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	$123.64	5.126%	$129.9778	$129.98	$130.00	$130.00
Purchase #2	$21.86	4.794%	$22.908	$22.91	$22.90	$22.90
Purchase #3	$215.68	11.393%	$240.2524	$240.25	$240.25	$240.30
Purchase #4	$237.43	10.571%	$262.5287	$262.53	$262.55	$262.50
Purchase #5	$118.61	7.501%	$127.5069	$127.51	$127.50	$127.50
Purchase #6	$72.96	4.659%	$76.3592	$76.36	$76.35	$76.40
Purchase #7	$66.78	5.317%	$70.3307	$70.33	$70.35	$70.30
7 purchase totals =	$856.96		$929.8637	$929.87	$929.90	$929.90