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	$161.89	13.771%	$184.1839	$184.18	$184.20	$184.20
Purchase #2	$199.53	3.511%	$206.5355	$206.54	$206.55	$206.50
Purchase #3	$187.60	4.612%	$196.2521	$196.25	$196.25	$196.30
Purchase #4	$56.69	7.361%	$60.863	$60.86	$60.85	$60.90
Purchase #5	$168.57	4.631%	$176.3765	$176.38	$176.40	$176.40
Purchase #6	$237.43	11.290%	$264.2358	$264.24	$264.25	$264.20
Purchase #7	$61.55	7.370%	$66.0862	$66.09	$66.10	$66.10
7 purchase totals =	$1,073.26		$1,154.5330	$1,154.54	$1,154.60	$1,154.60