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	$27.91	3.273%	$28.8235	$28.82	$28.80	$28.80
Purchase #2	$184.78	3.632%	$191.4912	$191.49	$191.50	$191.50
Purchase #3	$194.49	12.402%	$218.6106	$218.61	$218.60	$218.60
Purchase #4	$128.43	10.211%	$141.544	$141.54	$141.55	$141.50
Purchase #5	$216.66	3.655%	$224.5789	$224.58	$224.60	$224.60
Purchase #6	$99.59	13.435%	$112.9699	$112.97	$112.95	$113.00
Purchase #7	$130.69	8.712%	$142.0757	$142.08	$142.10	$142.10
7 purchase totals =	$982.55		$1,060.0938	$1,060.09	$1,060.10	$1,060.10