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	$213.52	8.459%	$231.5817	$231.58	$231.60	$231.60
Purchase #2	$221.78	11.828%	$248.0121	$248.01	$248.00	$248.00
Purchase #3	$204.62	5.213%	$215.2868	$215.29	$215.30	$215.30
Purchase #4	$45.78	6.170%	$48.6046	$48.60	$48.60	$48.60
Purchase #5	$101.71	11.645%	$113.5541	$113.55	$113.55	$113.60
Purchase #6	$209.69	4.830%	$219.818	$219.82	$219.80	$219.80
Purchase #7	$33.83	11.686%	$37.7834	$37.78	$37.80	$37.80
7 purchase totals =	$1,030.93		$1,114.6407	$1,114.63	$1,114.65	$1,114.70