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	$22.58	13.400%	$25.6057	$25.61	$25.60	$25.60
Purchase #2	$178.74	7.209%	$191.6254	$191.63	$191.65	$191.60
Purchase #3	$218.89	5.482%	$230.8895	$230.89	$230.90	$230.90
Purchase #4	$53.27	4.329%	$55.5761	$55.58	$55.60	$55.60
Purchase #5	$179.76	3.222%	$185.5519	$185.55	$185.55	$185.60
Purchase #6	$239.90	3.589%	$248.51	$248.51	$248.50	$248.50
Purchase #7	$78.73	3.353%	$81.3698	$81.37	$81.35	$81.40
7 purchase totals =	$971.87		$1,019.1284	$1,019.14	$1,019.15	$1,019.20