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	$224.56	11.702%	$250.838	$250.84	$250.85	$250.80
Purchase #2	$29.48	6.789%	$31.4814	$31.48	$31.50	$31.50
Purchase #3	$194.67	8.191%	$210.6154	$210.62	$210.60	$210.60
Purchase #4	$207.83	5.134%	$218.5	$218.50	$218.50	$218.50
Purchase #5	$165.62	11.723%	$185.0356	$185.04	$185.05	$185.00
Purchase #6	$206.96	7.688%	$222.8711	$222.87	$222.85	$222.90
Purchase #7	$134.52	6.872%	$143.7642	$143.76	$143.75	$143.80
7 purchase totals =	$1,163.64		$1,263.1057	$1,263.11	$1,263.10	$1,263.10