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	$202.67	3.454%	$209.6702	$209.67	$209.65	$209.70
Purchase #2	$29.69	10.282%	$32.7427	$32.74	$32.75	$32.70
Purchase #3	$78.98	6.163%	$83.8475	$83.85	$83.85	$83.80
Purchase #4	$97.27	4.160%	$101.3164	$101.32	$101.30	$101.30
Purchase #5	$215.28	10.508%	$237.9016	$237.90	$237.90	$237.90
Purchase #6	$80.47	12.519%	$90.544	$90.54	$90.55	$90.50
Purchase #7	$229.54	9.464%	$251.2637	$251.26	$251.25	$251.30
7 purchase totals =	$933.90		$1,007.2861	$1,007.28	$1,007.25	$1,007.20