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	$247.53	9.755%	$271.6766	$271.68	$271.70	$271.70
Purchase #2	$167.83	7.186%	$179.8903	$179.89	$179.90	$179.90
Purchase #3	$59.27	11.778%	$66.2508	$66.25	$66.25	$66.30
Purchase #4	$154.78	8.447%	$167.8543	$167.85	$167.85	$167.90
Purchase #5	$218.80	11.774%	$244.5615	$244.56	$244.55	$244.60
Purchase #6	$227.98	6.230%	$242.1832	$242.18	$242.20	$242.20
Purchase #7	$186.53	13.790%	$212.2525	$212.25	$212.25	$212.30
7 purchase totals =	$1,262.72		$1,384.6692	$1,384.66	$1,384.70	$1,384.90