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	$186.76	10.678%	$206.7022	$206.70	$206.70	$206.70
Purchase #2	$72.92	11.507%	$81.3109	$81.31	$81.30	$81.30
Purchase #3	$191.35	12.827%	$215.8945	$215.89	$215.90	$215.90
Purchase #4	$248.34	5.596%	$262.2371	$262.24	$262.25	$262.20
Purchase #5	$35.57	10.203%	$39.1992	$39.20	$39.20	$39.20
Purchase #6	$147.71	13.337%	$167.4101	$167.41	$167.40	$167.40
Purchase #7	$27.77	7.627%	$29.888	$29.89	$29.90	$29.90
7 purchase totals =	$910.42		$1,002.6420	$1,002.64	$1,002.65	$1,002.60