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	$233.55	13.868%	$265.9387	$265.94	$265.95	$265.90
Purchase #2	$163.98	13.621%	$186.3157	$186.32	$186.30	$186.30
Purchase #3	$18.91	11.443%	$21.0739	$21.07	$21.05	$21.10
Purchase #4	$242.60	12.126%	$272.0177	$272.02	$272.00	$272.00
Purchase #5	$172.41	3.451%	$178.3599	$178.36	$178.35	$178.40
Purchase #6	$109.56	3.368%	$113.25	$113.25	$113.25	$113.30
Purchase #7	$55.93	5.541%	$59.0291	$59.03	$59.05	$59.00
7 purchase totals =	$996.94		$1,095.9850	$1,095.99	$1,095.95	$1,096.00