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	$88.50	13.671%	$100.5988	$100.60	$100.60	$100.60
Purchase #2	$76.28	12.190%	$85.5785	$85.58	$85.60	$85.60
Purchase #3	$128.76	10.744%	$142.594	$142.59	$142.60	$142.60
Purchase #4	$98.96	3.379%	$102.3039	$102.30	$102.30	$102.30
Purchase #5	$48.82	5.435%	$51.4734	$51.47	$51.45	$51.50
Purchase #6	$172.54	3.806%	$179.1069	$179.11	$179.10	$179.10
Purchase #7	$114.73	8.659%	$124.6645	$124.66	$124.65	$124.70
7 purchase totals =	$728.59		$786.3200	$786.31	$786.30	$786.40