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	$147.98	9.261%	$161.6844	$161.68	$161.70	$161.70
Purchase #2	$234.59	13.164%	$265.4714	$265.47	$265.45	$265.50
Purchase #3	$229.26	11.729%	$256.1499	$256.15	$256.15	$256.10
Purchase #4	$72.48	13.840%	$82.5112	$82.51	$82.50	$82.50
Purchase #5	$101.98	11.668%	$113.879	$113.88	$113.90	$113.90
Purchase #6	$14.54	12.523%	$16.3608	$16.36	$16.35	$16.40
Purchase #7	$207.50	7.166%	$222.3695	$222.37	$222.35	$222.40
7 purchase totals =	$1,008.33		$1,118.4262	$1,118.42	$1,118.40	$1,118.50