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	$56.51	5.685%	$59.7226	$59.72	$59.70	$59.70
Purchase #2	$58.55	8.840%	$63.7258	$63.73	$63.75	$63.70
Purchase #3	$213.68	3.365%	$220.8703	$220.87	$220.85	$220.90
Purchase #4	$21.69	3.741%	$22.5014	$22.50	$22.50	$22.50
Purchase #5	$112.31	5.820%	$118.8464	$118.85	$118.85	$118.80
Purchase #6	$118.25	10.656%	$130.8507	$130.85	$130.85	$130.90
Purchase #7	$139.78	4.361%	$145.8758	$145.88	$145.90	$145.90
7 purchase totals =	$720.77		$762.3930	$762.40	$762.40	$762.40