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	$125.67	4.349%	$131.1354	$131.14	$131.15	$131.10
Purchase #2	$69.29	13.530%	$78.6649	$78.66	$78.65	$78.70
Purchase #3	$11.38	13.179%	$12.8798	$12.88	$12.90	$12.90
Purchase #4	$68.90	4.197%	$71.7917	$71.79	$71.80	$71.80
Purchase #5	$167.30	8.136%	$180.9115	$180.91	$180.90	$180.90
Purchase #6	$86.86	7.338%	$93.2338	$93.23	$93.25	$93.20
Purchase #7	$163.88	8.809%	$178.3162	$178.32	$178.30	$178.30
7 purchase totals =	$693.28		$746.9333	$746.93	$746.95	$746.90