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	$52.92	13.267%	$59.9409	$59.94	$59.95	$59.90
Purchase #2	$56.44	4.607%	$59.0402	$59.04	$59.05	$59.00
Purchase #3	$119.60	12.514%	$134.5667	$134.57	$134.55	$134.60
Purchase #4	$66.80	3.152%	$68.9055	$68.91	$68.90	$68.90
Purchase #5	$36.87	11.625%	$41.1561	$41.16	$41.15	$41.20
Purchase #6	$225.31	5.113%	$236.8301	$236.83	$236.85	$236.80
Purchase #7	$90.67	7.166%	$97.1674	$97.17	$97.15	$97.20
7 purchase totals =	$648.61		$697.6069	$697.62	$697.60	$697.60