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	$89.82	10.776%	$99.499	$99.50	$99.50	$99.50
Purchase #2	$55.67	12.277%	$62.5046	$62.50	$62.50	$62.50
Purchase #3	$112.41	8.811%	$122.3144	$122.31	$122.30	$122.30
Purchase #4	$45.55	4.387%	$47.5483	$47.55	$47.55	$47.50
Purchase #5	$5.28	12.393%	$5.9344	$5.93	$5.95	$5.90
Purchase #6	$50.64	11.387%	$56.4064	$56.41	$56.40	$56.40
Purchase #7	$6.95	4.844%	$7.2867	$7.29	$7.30	$7.30
7 purchase totals =	$366.32		$401.4938	$401.49	$401.50	$401.40