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	$211.63	12.648%	$238.397	$238.40	$238.40	$238.40
Purchase #2	$111.61	10.527%	$123.3592	$123.36	$123.35	$123.40
Purchase #3	$38.74	10.378%	$42.7604	$42.76	$42.75	$42.80
Purchase #4	$92.69	5.156%	$97.4691	$97.47	$97.45	$97.50
Purchase #5	$218.41	5.278%	$229.9377	$229.94	$229.95	$229.90
Purchase #6	$104.60	6.582%	$111.4848	$111.48	$111.50	$111.50
Purchase #7	$97.52	12.156%	$109.3745	$109.37	$109.35	$109.40
7 purchase totals =	$875.20		$952.7827	$952.78	$952.75	$952.90