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	$74.70	10.607%	$82.6234	$82.62	$82.60	$82.60
Purchase #2	$73.92	11.617%	$82.5073	$82.51	$82.50	$82.50
Purchase #3	$121.25	5.156%	$127.5017	$127.50	$127.50	$127.50
Purchase #4	$60.49	6.725%	$64.558	$64.56	$64.55	$64.60
Purchase #5	$124.71	11.820%	$139.4507	$139.45	$139.45	$139.50
Purchase #6	$91.46	5.443%	$96.4382	$96.44	$96.45	$96.40
Purchase #7	$109.43	13.288%	$123.9711	$123.97	$123.95	$124.00
7 purchase totals =	$655.96		$717.0504	$717.05	$717.00	$717.10