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	$92.73	8.206%	$100.3394	$100.34	$100.35	$100.30
Purchase #2	$152.32	8.184%	$164.7859	$164.79	$164.80	$164.80
Purchase #3	$19.85	7.729%	$21.3842	$21.38	$21.40	$21.40
Purchase #4	$54.32	3.846%	$56.4091	$56.41	$56.40	$56.40
Purchase #5	$150.68	7.347%	$161.7505	$161.75	$161.75	$161.80
Purchase #6	$162.27	13.710%	$184.5172	$184.52	$184.50	$184.50
Purchase #7	$210.54	6.266%	$223.7324	$223.73	$223.75	$223.70
7 purchase totals =	$842.71		$912.9187	$912.92	$912.95	$912.90