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	$66.70	6.219%	$70.8481	$70.85	$70.85	$70.80
Purchase #2	$151.61	11.278%	$168.7086	$168.71	$168.70	$168.70
Purchase #3	$99.57	5.143%	$104.6909	$104.69	$104.70	$104.70
Purchase #4	$106.94	3.840%	$111.0465	$111.05	$111.05	$111.00
Purchase #5	$238.54	8.866%	$259.689	$259.69	$259.70	$259.70
Purchase #6	$152.36	12.253%	$171.0287	$171.03	$171.05	$171.00
Purchase #7	$236.75	8.560%	$257.0158	$257.02	$257.00	$257.00
7 purchase totals =	$1,052.47		$1,143.0276	$1,143.04	$1,143.05	$1,142.90