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	$114.44	8.264%	$123.8973	$123.90	$123.90	$123.90
Purchase #2	$157.34	3.567%	$162.9523	$162.95	$162.95	$163.00
Purchase #3	$154.59	13.402%	$175.3082	$175.31	$175.30	$175.30
Purchase #4	$72.36	12.744%	$81.5816	$81.58	$81.60	$81.60
Purchase #5	$12.75	12.295%	$14.3176	$14.32	$14.30	$14.30
Purchase #6	$163.33	5.383%	$172.1221	$172.12	$172.10	$172.10
Purchase #7	$49.74	13.254%	$56.3325	$56.33	$56.35	$56.30
7 purchase totals =	$724.55		$786.5116	$786.51	$786.50	$786.50