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	$192.58	9.405%	$210.6921	$210.69	$210.70	$210.70
Purchase #2	$133.65	12.494%	$150.3482	$150.35	$150.35	$150.30
Purchase #3	$66.81	8.467%	$72.4668	$72.47	$72.45	$72.50
Purchase #4	$144.82	3.631%	$150.0784	$150.08	$150.10	$150.10
Purchase #5	$89.83	12.265%	$100.8476	$100.85	$100.85	$100.80
Purchase #6	$18.53	6.849%	$19.7991	$19.80	$19.80	$19.80
Purchase #7	$35.98	3.775%	$37.3382	$37.34	$37.35	$37.30
7 purchase totals =	$682.20		$741.5704	$741.58	$741.60	$741.50