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	$52.87	6.153%	$56.1231	$56.12	$56.10	$56.10
Purchase #2	$31.62	4.613%	$33.0786	$33.08	$33.10	$33.10
Purchase #3	$83.28	7.759%	$89.7417	$89.74	$89.75	$89.70
Purchase #4	$74.32	12.746%	$83.7928	$83.79	$83.80	$83.80
Purchase #5	$223.65	6.661%	$238.5473	$238.55	$238.55	$238.50
Purchase #6	$128.57	6.126%	$136.4462	$136.45	$136.45	$136.40
Purchase #7	$93.25	4.649%	$97.5852	$97.59	$97.60	$97.60
7 purchase totals =	$687.56		$735.3149	$735.32	$735.35	$735.20