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	$180.46	9.122%	$196.9216	$196.92	$196.90	$196.90
Purchase #2	$17.89	7.563%	$19.243	$19.24	$19.25	$19.20
Purchase #3	$215.37	4.360%	$224.7601	$224.76	$224.75	$224.80
Purchase #4	$88.69	5.496%	$93.5644	$93.56	$93.55	$93.60
Purchase #5	$69.29	11.608%	$77.3332	$77.33	$77.35	$77.30
Purchase #6	$116.78	5.830%	$123.5883	$123.59	$123.60	$123.60
Purchase #7	$96.50	6.579%	$102.8487	$102.85	$102.85	$102.80
7 purchase totals =	$784.98		$838.2593	$838.25	$838.25	$838.20