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	$80.43	6.225%	$85.4368	$85.44	$85.45	$85.40
Purchase #2	$215.31	10.748%	$238.4515	$238.45	$238.45	$238.50
Purchase #3	$76.66	12.756%	$86.4387	$86.44	$86.45	$86.40
Purchase #4	$185.97	5.792%	$196.7414	$196.74	$196.75	$196.70
Purchase #5	$74.68	9.386%	$81.6895	$81.69	$81.70	$81.70
Purchase #6	$209.25	10.145%	$230.4784	$230.48	$230.50	$230.50
Purchase #7	$133.26	3.799%	$138.3225	$138.32	$138.30	$138.30
7 purchase totals =	$975.56		$1,057.5588	$1,057.56	$1,057.60	$1,057.50