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	$225.86	3.385%	$233.5054	$233.51	$233.50	$233.50
Purchase #2	$62.66	5.520%	$66.1188	$66.12	$66.10	$66.10
Purchase #3	$140.41	4.838%	$147.203	$147.20	$147.20	$147.20
Purchase #4	$103.70	8.308%	$112.3154	$112.32	$112.30	$112.30
Purchase #5	$98.64	12.836%	$111.3014	$111.30	$111.30	$111.30
Purchase #6	$155.74	7.317%	$167.1355	$167.14	$167.15	$167.10
Purchase #7	$27.57	5.648%	$29.1272	$29.13	$29.15	$29.10
7 purchase totals =	$814.58		$866.7067	$866.72	$866.70	$866.60