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	$115.50	6.737%	$123.2812	$123.28	$123.30	$123.30
Purchase #2	$180.61	7.178%	$193.5742	$193.57	$193.55	$193.60
Purchase #3	$201.60	11.246%	$224.2719	$224.27	$224.25	$224.30
Purchase #4	$58.70	3.118%	$60.5303	$60.53	$60.55	$60.50
Purchase #5	$39.50	7.599%	$42.5016	$42.50	$42.50	$42.50
Purchase #6	$241.38	7.511%	$259.5101	$259.51	$259.50	$259.50
Purchase #7	$203.84	11.535%	$227.3529	$227.35	$227.35	$227.40
7 purchase totals =	$1,041.13		$1,131.0222	$1,131.01	$1,131.00	$1,131.10