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	$232.76	11.611%	$259.7858	$259.79	$259.80	$259.80
Purchase #2	$82.54	9.399%	$90.2979	$90.30	$90.30	$90.30
Purchase #3	$18.85	9.374%	$20.617	$20.62	$20.60	$20.60
Purchase #4	$117.93	5.407%	$124.3065	$124.31	$124.30	$124.30
Purchase #5	$202.31	3.300%	$208.9862	$208.99	$209.00	$209.00
Purchase #6	$94.52	5.217%	$99.4511	$99.45	$99.45	$99.50
Purchase #7	$194.32	9.621%	$213.0155	$213.02	$213.00	$213.00
7 purchase totals =	$943.23		$1,016.4600	$1,016.48	$1,016.45	$1,016.50