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	$96.89	9.115%	$105.7215	$105.72	$105.70	$105.70
Purchase #2	$123.95	7.224%	$132.9041	$132.90	$132.90	$132.90
Purchase #3	$136.80	7.291%	$146.7741	$146.77	$146.75	$146.80
Purchase #4	$239.61	12.246%	$268.9526	$268.95	$268.95	$269.00
Purchase #5	$55.98	13.142%	$63.3369	$63.34	$63.35	$63.30
Purchase #6	$94.57	11.465%	$105.4125	$105.41	$105.40	$105.40
Purchase #7	$229.75	3.798%	$238.4759	$238.48	$238.50	$238.50
7 purchase totals =	$977.55		$1,061.5776	$1,061.57	$1,061.55	$1,061.60