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	$155.49	5.272%	$163.6874	$163.69	$163.70	$163.70
Purchase #2	$73.73	6.307%	$78.3802	$78.38	$78.40	$78.40
Purchase #3	$30.91	10.789%	$34.2449	$34.24	$34.25	$34.20
Purchase #4	$13.38	8.438%	$14.509	$14.51	$14.50	$14.50
Purchase #5	$153.78	10.104%	$169.3179	$169.32	$169.30	$169.30
Purchase #6	$169.39	13.295%	$191.9104	$191.91	$191.90	$191.90
Purchase #7	$211.57	10.344%	$233.4548	$233.45	$233.45	$233.50
7 purchase totals =	$808.25		$885.5046	$885.50	$885.50	$885.50