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	$204.64	3.347%	$211.4893	$211.49	$211.50	$211.50
Purchase #2	$204.92	10.841%	$227.1354	$227.14	$227.15	$227.10
Purchase #3	$30.47	9.867%	$33.4765	$33.48	$33.50	$33.50
Purchase #4	$182.69	8.530%	$198.2735	$198.27	$198.25	$198.30
Purchase #5	$17.98	13.520%	$20.4109	$20.41	$20.40	$20.40
Purchase #6	$111.66	10.618%	$123.5161	$123.52	$123.50	$123.50
Purchase #7	$233.85	9.300%	$255.5981	$255.60	$255.60	$255.60
7 purchase totals =	$986.21		$1,069.8998	$1,069.91	$1,069.90	$1,069.90