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	$153.86	9.546%	$168.5475	$168.55	$168.55	$168.50
Purchase #2	$26.39	10.443%	$29.1459	$29.15	$29.15	$29.10
Purchase #3	$184.73	13.435%	$209.5485	$209.55	$209.55	$209.50
Purchase #4	$41.86	3.621%	$43.3758	$43.38	$43.40	$43.40
Purchase #5	$88.49	12.632%	$99.6681	$99.67	$99.65	$99.70
Purchase #6	$102.40	5.246%	$107.7719	$107.77	$107.75	$107.80
Purchase #7	$104.99	5.248%	$110.4999	$110.50	$110.50	$110.50
7 purchase totals =	$702.72		$768.5576	$768.57	$768.55	$768.50