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	$117.81	7.415%	$126.5456	$126.55	$126.55	$126.50
Purchase #2	$112.76	3.485%	$116.6897	$116.69	$116.70	$116.70
Purchase #3	$45.29	11.638%	$50.5609	$50.56	$50.55	$50.60
Purchase #4	$209.43	7.227%	$224.5655	$224.57	$224.55	$224.60
Purchase #5	$206.60	4.203%	$215.2834	$215.28	$215.30	$215.30
Purchase #6	$82.56	4.811%	$86.532	$86.53	$86.55	$86.50
Purchase #7	$236.96	11.373%	$263.9095	$263.91	$263.90	$263.90
7 purchase totals =	$1,011.41		$1,084.0866	$1,084.09	$1,084.10	$1,084.10