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	$108.74	7.725%	$117.1402	$117.14	$117.15	$117.10
Purchase #2	$123.61	3.172%	$127.5309	$127.53	$127.55	$127.50
Purchase #3	$190.49	7.698%	$205.1539	$205.15	$205.15	$205.20
Purchase #4	$113.40	6.141%	$120.3639	$120.36	$120.35	$120.40
Purchase #5	$183.51	8.708%	$199.4901	$199.49	$199.50	$199.50
Purchase #6	$226.69	4.591%	$237.0973	$237.10	$237.10	$237.10
Purchase #7	$11.87	8.516%	$12.8808	$12.88	$12.90	$12.90
7 purchase totals =	$958.31		$1,019.6571	$1,019.65	$1,019.70	$1,019.70