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	$198.35	7.593%	$213.4107	$213.41	$213.40	$213.40
Purchase #2	$227.79	9.748%	$249.995	$250.00	$250.00	$250.00
Purchase #3	$102.36	7.260%	$109.7913	$109.79	$109.80	$109.80
Purchase #4	$103.56	11.182%	$115.1401	$115.14	$115.15	$115.10
Purchase #5	$81.83	10.823%	$90.6865	$90.69	$90.70	$90.70
Purchase #6	$109.80	3.450%	$113.5881	$113.59	$113.60	$113.60
Purchase #7	$186.25	11.407%	$207.4955	$207.50	$207.50	$207.50
7 purchase totals =	$1,009.94		$1,100.1072	$1,100.12	$1,100.15	$1,100.10