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	$190.29	12.165%	$213.4388	$213.44	$213.45	$213.40
Purchase #2	$67.81	4.104%	$70.5929	$70.59	$70.60	$70.60
Purchase #3	$36.71	7.723%	$39.5451	$39.55	$39.55	$39.50
Purchase #4	$59.25	8.709%	$64.4101	$64.41	$64.40	$64.40
Purchase #5	$18.54	4.692%	$19.4099	$19.41	$19.40	$19.40
Purchase #6	$70.49	3.466%	$72.9332	$72.93	$72.95	$72.90
Purchase #7	$77.36	11.170%	$86.0011	$86.00	$86.00	$86.00
7 purchase totals =	$520.45		$566.3311	$566.33	$566.35	$566.20