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	$45.77	13.607%	$51.9979	$52.00	$52.00	$52.00
Purchase #2	$112.31	3.577%	$116.3273	$116.33	$116.35	$116.30
Purchase #3	$206.70	4.417%	$215.8299	$215.83	$215.85	$215.80
Purchase #4	$211.26	3.596%	$218.8569	$218.86	$218.85	$218.90
Purchase #5	$236.94	8.827%	$257.8547	$257.85	$257.85	$257.90
Purchase #6	$238.81	12.467%	$268.5824	$268.58	$268.60	$268.60
Purchase #7	$92.25	7.723%	$99.3745	$99.37	$99.35	$99.40
7 purchase totals =	$1,144.04		$1,228.8236	$1,228.82	$1,228.85	$1,228.90