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	$78.30	5.697%	$82.7608	$82.76	$82.75	$82.80
Purchase #2	$179.41	3.666%	$185.9872	$185.99	$186.00	$186.00
Purchase #3	$195.44	6.652%	$208.4407	$208.44	$208.45	$208.40
Purchase #4	$29.59	9.607%	$32.4327	$32.43	$32.45	$32.40
Purchase #5	$25.66	12.530%	$28.8752	$28.88	$28.90	$28.90
Purchase #6	$111.25	6.343%	$118.3066	$118.31	$118.30	$118.30
Purchase #7	$82.73	5.764%	$87.4986	$87.50	$87.50	$87.50
7 purchase totals =	$702.38		$744.3018	$744.31	$744.35	$744.30