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	$217.90	7.195%	$233.5779	$233.58	$233.60	$233.60
Purchase #2	$171.50	4.169%	$178.6498	$178.65	$178.65	$178.60
Purchase #3	$165.83	12.121%	$185.9303	$185.93	$185.95	$185.90
Purchase #4	$211.92	10.237%	$233.6143	$233.61	$233.60	$233.60
Purchase #5	$82.95	7.144%	$88.8759	$88.88	$88.90	$88.90
Purchase #6	$52.43	5.644%	$55.3891	$55.39	$55.40	$55.40
Purchase #7	$49.43	12.669%	$55.6923	$55.69	$55.70	$55.70
7 purchase totals =	$951.96		$1,031.7296	$1,031.73	$1,031.80	$1,031.70