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	$68.96	13.393%	$78.1958	$78.20	$78.20	$78.20
Purchase #2	$28.89	11.627%	$32.249	$32.25	$32.25	$32.20
Purchase #3	$60.42	3.461%	$62.5111	$62.51	$62.50	$62.50
Purchase #4	$227.78	13.790%	$259.1909	$259.19	$259.20	$259.20
Purchase #5	$49.27	12.463%	$55.4105	$55.41	$55.40	$55.40
Purchase #6	$241.69	9.785%	$265.3394	$265.34	$265.35	$265.30
Purchase #7	$156.76	5.745%	$165.7659	$165.77	$165.75	$165.80
7 purchase totals =	$833.77		$918.6626	$918.67	$918.65	$918.60