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	$203.67	7.723%	$219.3994	$219.40	$219.40	$219.40
Purchase #2	$48.98	12.533%	$55.1187	$55.12	$55.10	$55.10
Purchase #3	$5.91	3.108%	$6.0937	$6.09	$6.10	$6.10
Purchase #4	$34.72	3.323%	$35.8737	$35.87	$35.85	$35.90
Purchase #5	$176.50	5.543%	$186.2834	$186.28	$186.30	$186.30
Purchase #6	$142.90	4.164%	$148.8504	$148.85	$148.85	$148.90
Purchase #7	$80.85	10.733%	$89.5276	$89.53	$89.55	$89.50
7 purchase totals =	$693.53		$741.1469	$741.14	$741.15	$741.20