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	$206.71	12.151%	$231.8273	$231.83	$231.85	$231.80
Purchase #2	$16.44	11.190%	$18.2796	$18.28	$18.30	$18.30
Purchase #3	$79.54	11.864%	$88.9766	$88.98	$89.00	$89.00
Purchase #4	$99.57	9.511%	$109.0401	$109.04	$109.05	$109.00
Purchase #5	$196.30	8.854%	$213.6804	$213.68	$213.70	$213.70
Purchase #6	$222.40	13.223%	$251.808	$251.81	$251.80	$251.80
Purchase #7	$96.63	12.398%	$108.6102	$108.61	$108.60	$108.60
7 purchase totals =	$917.59		$1,022.2222	$1,022.23	$1,022.30	$1,022.20