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	$41.54	6.667%	$44.3095	$44.31	$44.30	$44.30
Purchase #2	$72.92	5.469%	$76.908	$76.91	$76.90	$76.90
Purchase #3	$178.61	11.176%	$198.5715	$198.57	$198.55	$198.60
Purchase #4	$28.53	4.641%	$29.8541	$29.85	$29.85	$29.90
Purchase #5	$54.47	6.286%	$57.894	$57.89	$57.90	$57.90
Purchase #6	$88.98	11.801%	$99.4805	$99.48	$99.50	$99.50
Purchase #7	$96.78	11.513%	$107.9223	$107.92	$107.90	$107.90
7 purchase totals =	$561.83		$614.9399	$614.93	$614.90	$615.00