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	$38.61	12.213%	$43.3254	$43.33	$43.35	$43.30
Purchase #2	$172.49	8.843%	$187.7433	$187.74	$187.75	$187.70
Purchase #3	$124.68	9.577%	$136.6206	$136.62	$136.60	$136.60
Purchase #4	$106.40	6.365%	$113.1724	$113.17	$113.15	$113.20
Purchase #5	$204.38	9.319%	$223.4262	$223.43	$223.45	$223.40
Purchase #6	$223.76	7.300%	$240.0945	$240.09	$240.10	$240.10
Purchase #7	$196.88	13.605%	$223.6655	$223.67	$223.65	$223.70
7 purchase totals =	$1,067.20		$1,168.0479	$1,168.05	$1,168.05	$1,168.00