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	$55.29	7.449%	$59.4086	$59.41	$59.40	$59.40
Purchase #2	$241.50	11.565%	$269.4295	$269.43	$269.45	$269.40
Purchase #3	$221.42	8.608%	$240.4798	$240.48	$240.50	$240.50
Purchase #4	$89.44	13.594%	$101.5985	$101.60	$101.60	$101.60
Purchase #5	$118.87	7.785%	$128.124	$128.12	$128.10	$128.10
Purchase #6	$217.79	7.235%	$233.5471	$233.55	$233.55	$233.50
Purchase #7	$201.76	3.327%	$208.4726	$208.47	$208.45	$208.50
7 purchase totals =	$1,146.07		$1,241.0601	$1,241.06	$1,241.05	$1,241.00