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	$213.45	4.292%	$222.6113	$222.61	$222.60	$222.60
Purchase #2	$180.81	7.636%	$194.6167	$194.62	$194.60	$194.60
Purchase #3	$36.78	3.412%	$38.0349	$38.03	$38.05	$38.00
Purchase #4	$85.39	12.692%	$96.2277	$96.23	$96.25	$96.20
Purchase #5	$30.36	13.425%	$34.4358	$34.44	$34.45	$34.40
Purchase #6	$188.31	11.305%	$209.5984	$209.60	$209.60	$209.60
Purchase #7	$46.92	11.788%	$52.4509	$52.45	$52.45	$52.50
7 purchase totals =	$782.02		$847.9757	$847.98	$848.00	$847.90