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	$88.45	3.341%	$91.4051	$91.41	$91.40	$91.40
Purchase #2	$10.73	8.257%	$11.616	$11.62	$11.60	$11.60
Purchase #3	$13.31	12.433%	$14.9648	$14.96	$14.95	$15.00
Purchase #4	$64.69	5.776%	$68.4265	$68.43	$68.45	$68.40
Purchase #5	$120.89	9.759%	$132.6877	$132.69	$132.70	$132.70
Purchase #6	$173.86	6.573%	$185.2878	$185.29	$185.30	$185.30
Purchase #7	$84.54	5.525%	$89.2108	$89.21	$89.20	$89.20
7 purchase totals =	$556.47		$593.5987	$593.61	$593.60	$593.60