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	$213.61	4.791%	$223.8441	$223.84	$223.85	$223.80
Purchase #2	$38.78	8.779%	$42.1845	$42.18	$42.20	$42.20
Purchase #3	$142.77	3.515%	$147.7884	$147.79	$147.80	$147.80
Purchase #4	$182.39	3.332%	$188.4672	$188.47	$188.45	$188.50
Purchase #5	$198.92	9.597%	$218.0104	$218.01	$218.00	$218.00
Purchase #6	$54.35	12.810%	$61.3122	$61.31	$61.30	$61.30
Purchase #7	$125.78	3.374%	$130.0238	$130.02	$130.00	$130.00
7 purchase totals =	$956.60		$1,011.6306	$1,011.62	$1,011.60	$1,011.60