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	$194.32	3.160%	$200.4605	$200.46	$200.45	$200.50
Purchase #2	$36.45	11.783%	$40.7449	$40.74	$40.75	$40.70
Purchase #3	$105.31	6.391%	$112.0404	$112.04	$112.05	$112.00
Purchase #4	$69.58	4.494%	$72.7069	$72.71	$72.70	$72.70
Purchase #5	$237.30	7.308%	$254.6419	$254.64	$254.65	$254.60
Purchase #6	$164.93	6.686%	$175.9572	$175.96	$175.95	$176.00
Purchase #7	$92.34	12.381%	$103.7726	$103.77	$103.75	$103.80
7 purchase totals =	$900.23		$960.3244	$960.32	$960.30	$960.30