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	$134.97	6.222%	$143.3678	$143.37	$143.35	$143.40
Purchase #2	$62.87	12.227%	$70.5571	$70.56	$70.55	$70.60
Purchase #3	$190.62	10.456%	$210.5512	$210.55	$210.55	$210.60
Purchase #4	$102.52	7.152%	$109.8522	$109.85	$109.85	$109.90
Purchase #5	$171.45	7.626%	$184.5248	$184.52	$184.50	$184.50
Purchase #6	$212.86	6.803%	$227.3409	$227.34	$227.35	$227.30
Purchase #7	$86.36	3.710%	$89.564	$89.56	$89.55	$89.60
7 purchase totals =	$961.65		$1,035.7580	$1,035.75	$1,035.70	$1,035.90